In this post I have gathered some (not all) of the info gathered from various sources (including Serb's and Storm's posts on RU forums).
It's obvious that the hull size and design of E-50/75 is similar to the one of King Tiger, which leaves nearly no space for rear transmission layout declared by Jentz and Doyle in their reconstruction blueprints.
The real archive blueprints are still not public and probably will never be.
Serb: Rear engine layout (which results from intakes), the design of leading and rear wheels (plus the absence of hub drive casing) make the rear-drive for E-50/75 impossible. In the generally accepted configuration and design provided by Doyle and Jentz at least.
There is no evidence in the form of engineering blueprints, based on Doyle's hull geometry, that could demonstrate the possibility of moving the transmission to the rear. The above does mean that with quite high probability Jentz and Doyle actually presented the two mutually exclusive theses on the same page.
Consequently the conventional front-drive design is considered to be more viable, without denying possible intentions of engineering rear-drive E-50/75.
More evidence by Serb is to be presented.
Storm: It's known that French AMX 50B was a successor of German tanks in terms of design. Still the hull of Tiger II is 6.4m (it's ~7.3m), while AMX 50B is almost 1m longer (7.35m). That allowed French engineers to enable rear-drive for that very vehicle, while E-series were almost of identical size with KT. The difference was mainly in armour thickness and slope.
If we cut 1m from AMX 50B hull we are getting the following:
That leaves very little space for driver or engine compartment. There was no way the turret could be in the center of the hull.
Added Panther II turret, leaving the suspension, AMX 50B hull decreased by 90cm:
Looks somewhat horrible.
With the current front armour values of E-50 (upper 120@60, lower 120@60) and E-75 (upper 160@60, lower 130@60) the made adjustment doesn't look drastic and is not supposed to lead to noticeable performance decrease. However if the performance of either of the above drops, the necessary buffs will follow.
Edited (June 7):
Regarding the nerf thing, let's do some math.
transmission is about 25% of the vertical projection of E-50/75 (I bet
this is overestimation), internal module has 33% chance of being damaged
and engine's (Maybach HL 295 Ausf. A) chance of fire is 15%, we get the
accounts only for penetrating shots, while even at high tiers pen chance
is not even close to 100% (for front hits ofc). It would be more
difficult to do the same from the side.
So how many shots do we need to set a tank on fire:
rounds with average damage of 300 (it might be low for high tiers) will
inflict 24242 damage which is enough to destroy E-75/50 how many times?