Here's an idea I had for a large-scale upgrade to the Leopard chassis in the late 90s or early 2000s. The original MB873 is very large (47 L displacement) and takes up a lot of volume in the rear of the hull. The Leopard 2 also has a relatively small turret, which is constrained by the position of the firewall to the rear and forces the driver to be pushed to the side of the hull. The size of the turret means that about 2/3 of the ammunition is stored in the hull front; I don't know whether it is blowout-protected.
The EuroPowerPack uses a much smaller (27 L displacement) MB883 V12 to generate the same power as the MB873. The engine itself is 300 mm shorter, but the smaller size means it can be mounted transversely in the hull, which saves up to a meter of space. This could be used to shorten and lighten the hull, or it could be used to fit a wider turret ring. The EuroPowerPack was used in UAE Leclercs as a replacement for hyperbar V8s, indicative of the smaller size, and in the Merkava 4 around 2000. It was also used in the Challenger 2E, which I suspect was designed in response to the horrendous failure of the Challenger 2 compared to the M1 in the Kuwaiti trials after the Gulf War.
The extra space permitted by a smaller powerpack would allow the width of the vehicle, rather than the length available, to be the limiting factor for turret ring diameter. An increase from the Leopard 1/Leopard 2/K1/Osorio 1980 mm to the M48/M60/Chieftain/Challenger/M1 2159 mm would not be out of the question, nor would an even larger turret ring. Even an increase of 300 mm would put the front of the turret ring two feet farther back, which would allow the driver to move to the center of the hull. The actual Leopard 2-140 was a kludge like the Object 292, but something with a giant turret like the CATTB would be more feasible. I know it's the 90s here, but maybe the concept of a transverse-mount 1,500 hp motor could be brought earlier with better support and could slide in with an order in 1990 or 1991.
EDIT: I almost forgot to mention my inspiration.