Here's a few vehicles I made specifically for the Alt-WW2 AU.
Starting off with German vehicles.
E-50 Coeelion is simply the E-50 with the Panther Coelion turret with 3,7cm AA guns.
The E-50 Falke is an AA tank with twin 5,5cm guns.
The Jagdpanzer auf E-50 is a tank destroyer with a rear-mounted 88mm L71 gun on the E-50 chassis.
Not really meant for the AU, but just for fun, is the E-50M, an E-50 with rear transmission which reduces the height of the hull.
The Jagdpanzer auf E-75 is a heavy tank destroyer using the E-75 chassis for a rear-mounted 12,8cm gun.
The Sturmgeschütz auf E-100 comes in two flavours, a mid-mounted 15cm gun (considered by some as the more realistic version), and a rear-mounted 17cm gun (ie the WoT version)
For Hungary there's the very much fake, bur nonetheless cool 44M Tas Rohamlöveg tank destroyer with a lon 75mm anti-tank gun.
For Italy I made up a Panther-based hull with the Italian torsion-bar design from the P43ter with an enlarged turret to better handle the long 90mm gun.
The Ho-To is a tank destroyer variant of the Type 4 Chi-To.
Despite being somewhat real, though the exact details regarding their appearance is somewhat unclear, I'll post them here for certain, and that being the Chi-Ri based tank destroyers armed with a 10,5cm gun, the Ho-Ri. Irl there were designs for a rear-mounted version, and a mid-mounted version. The real mockup features heavily sloped armor, but the drawings made of both show the same front as the Chi-Ri, still including the 3,7cm gun in the front.
This one is also technically real, though with some modifications. There were two designs for the 20TP KSUST, the difference being the engine, and its size. In my AU the KSUST 2 design also has the modified turret mounting the Wz.24 75mm AA gun instead of the 1897 75mm field gun.
Based on a real design, though not in appearance is the last hurrah of the Polish cruiser tanks, the 25TP. It has the same 1924 75mm AA gun as the KSUST 2, but on a much more modern hull with thicker armor and better mobility.
The US Army did test the 90mm gun on the M6 irl, same with the T20-series, and in both cases it was found that though they did indeed fit, and work without overstressing the vehicles and/or the suspensions, the fit was a little too snug, hence the rejection of the 90mm gun on said tanks. I decided to make a version of the M6 using the T25 turret in place of the M6s' turret to better accomodate the 90mm gun. This is done to keep the M6 tank more relevant into the mid-late 40s while the M25 (as a stop-gap medium tank,) the M26 medium tank and the M32 heavy tank enters service taking over the most pressing front-line needs from the earlier tanks.
Though based on the WoT idea of a casemated TD based on the T25 chassis, it does make some sense, at least in my AU where there would be plenty of M25 chassis to convert into a TD using the long 90mm gun to create a TF that could take out all but the most heavily armored tanks, such as the E-75 and E-100. I don't quite see how I'm gonna make a turreted TD with either the long 90 or 105mm gun, that is both light and mobile enough, hence the casemated design.
The T-43-85 basically replaces the T-34 as the tank of choice of the Soviet army, being supplemented by the more advanced T-44 tank. The T-43 did have a 76mm gun irl, but the 85mm gun would go along well with making the T-43 more worthwhile since its turret can better handle that gun.