stancrist said:

However, they also can be equipped with rifles or carbines, just as they were in World War II.

During WW2 no army that I am aware of did equip their AFVs with rifles. Only the US issued carbines (since no other nation had a similar weapon).
The German army did issue SMGs. But the most universal issued small arm for AFV during WW2 have been pistols or none at all.

stancrist said:

How would it compromise ground force effectiveness by changing the configuration of tanks from rear engine to front engine?

The engine in back layout is inefficient. It creates a higher hull, causes difficulties in armoring the front, results in exposed air intakes and exhaust, has negative impact on the gun elevation in the frontal arc etc. The list goes on.
There is a reason why on one nation has build an MBT with this layout. It was tried time and again by everyone else and found inferiour. The Merkava is a very special vehicle. Its optimised for the tactical and operational situation of Israel and for the terrain there. This means the Merkava is conciderable less usefull everywhere else. Which is why nobody was ever intrested in buying it or building it in license. Its simply not a good layout for the requirements of the vast majority of tank building nations.

schnuersi said:

       stancrist said: However, they also can be equipped with rifles or carbines, just as they were in World War II.

During WW2 no army that I am aware of did equip their AFVs with rifles.

I meant all of the non-infantry types except tank crewmen.  Only tankers need a compact PDW.  All others can be armed with rifle, carbine, or SBR.

stancrist said:

I meant all of the non-infantry types except tank crewmen.

Make that vehicle crewmen and i agree... but then you have allmost everybody exept infantry.

stancrist said:

All others can be armed with rifle, carbine, or SBR.

There are lots of people in an army that do not need a rifle and for whom a carbine would interfere with the main task.

And yes during WW2 allmost everybody carried a rifle which lead to a lot a situations where non infantry personel got caught without any weapon at hand because a rifle is to large and unwieldy to be carried around all the time while doing something other than being an infantry man. The US came up with the carbine because they realised this. The carbine is still to large for most tasks.

schnuersi said:

       stancrist said: I meant all of the non-infantry types except tank crewmen.

Make that vehicle crewmen and i agree... but then you have allmost everybody exept infantry.

LOL.  There are a great number of soldiers who are neither infantry nor AFV crewmen.  Army MOS List: Full List of Army Jobs - HoodMWR

schnuersi said:

       stancrist said: All others can be armed with rifle, carbine, or SBR.

There are lots of people in an army that do not need a rifle and for whom a carbine would interfere with the main task.

Such as?

schnuersi said:

And yes during WW2 allmost everybody carried a rifle which lead to a lot a situations where non infantry personel got caught without any weapon at hand because a rifle is to large and unwieldy to be carried around all the time while doing something other than being an infantry man.

Can you cite any examples?

stancrist said:

LOL. There are a great number of soldiers who are neither infantry nor AFV crewmen.

No but they are vehicle crew... allmost everybody drives around in a vehicle and most task are even conducted while in the vehicle. If the vehicle is armored or is unimportant.

stancrist said:

Such as?

Engineers, medics, artillery men, signals guys, mechanics the list goes on.

stancrist said:

Can you cite any examples?

For non infantry soldiers getting jumped while they did not have a rifle nearby?
In the training manual of the German army used to be such examples. It also was a common occurence during training. People who where issued rifles frequently left them in their vehicle or put them somewhere where they would not get lost and ended up being unarmed in a supprise contact.
But you can easily google pictures of basically any German support arm during WW2 and usually you see a peculiar absent of small arms when the non infantry soldiers do their work. For example artillery, AA gun and AT gun crews.

schnuersi said:

       stancrist said: LOL. There are a great number of soldiers who are neither infantry nor AFV crewmen.

No but they are vehicle crew... allmost everybody drives around in a vehicle and most task are even conducted while in the vehicle. If the vehicle is armored or is unimportant.

Well, if you're going to define "vehicle crewman" as any soldier who drives a motor vehicle at some time during the year, then that means even infantrymen are vehicle crewman and should have a PDW instead of a rifle or machine gun...

schnuersi said:

       stancrist said: Such as?

Engineers, medics, artillery men, signals guys, mechanics the list goes on.

US Army medics are armed with a carbine, but it does not seem to impede them in performing their duties. 

And I see no reason why a carbine would be any more incompatible with the other jobs than would an MP7.

schnuersi said:

       stancrist said: Can you cite any examples?

For non infantry soldiers getting jumped while they did not have a rifle nearby? In the training manual of the German army used to be such examples. It also was a common occurence during training. People who where issued rifles frequently left them in their vehicle or put them somewhere where they would not get lost and ended up being unarmed in a supprise contact.

I meant examples from combat.  Peacetime training exercises don't matter.  In peacetime, soldiers do stuff they probably wouldn't on the battlefield.  During one deployment to the National Training Center, some of the guys in my battalion stowed folding beach chairs and coolers full of beer in the bustle racks of their tanks, then "kicked back" and relaxed with a cold brew in the evening.

schnuersi said:

But you can easily google pictures of basically any German support arm during WW2 and usually you see a peculiar absent of small arms when the non infantry soldiers do their work. For example artillery, AA gun and AT gun crews.

That's not even a little peculiar.  That's actually quite typical.  You see the same absence of small arms in most WW2 photos of US artillery in action.  For example:

It's still the same in the 21st century.

YouTube

US Marines Fire Howitzer 155mm in Afghanistan

US Marines Fire M777 Howitzer 155mm at enemy targets in Afghanistan. The M777 howitzer is a towed 155 mm artillery piece, successor to the M198 howitzer in t...

It’s almost like those redlegs put their rifles down out of the way to operate the guns. Just like they’d put down any slung weapon. Most likely they would rather remove a holster and pistol as well; belt holsters, sidearms and spare mags still get in the way when you’re moving around.

Engineers are vehicle crew? I must let my engineer acquaintances know that. 

DavidPawley said:

It’s almost like those redlegs put their rifles down out of the way to operate the guns. Just like they’d put down any slung weapon.

Yup, it's exactly like that.

I agree they would put down any slung weapon, even one as relatively small and light as the MP7.

DavidPawley said:

Most likely they would rather remove a holster and pistol as well; belt holsters, sidearms and spare mags still get in the way when you’re moving around.

Hard to say for sure.  It looks like the M1 carbine was the standard personal weapon for artillery gun crews in WW2.  https://youtu.be/1QgXuhv7-54?t=1501

I only found one photo showing an artillery man who appears to have a holstered pistol (at far left, below), but he is not one of the ammunition handlers.

Position of the slung weapon may be dependent on the chances of the enemy infantry suddenly popping out near your position

One thing is manning a howitzer or any other artillery piece well back of the actual front line, and another pushing it way up front in the infantry support role, or while defending the forward position