I'm far from an expert on anything, but I think that as long as you stick to what I call "regular" .45 Super, you won't need any upgrades really. The one thing I do know is that stock Glock .45 barrels have some pretty lousy chamber support, which isn't much of an issue when you're dealing with the lower pressure .45 ACP, but could bring about some concerns when pressures go up. Comparatively the 10mm G20 has better chamber support than the G21 .45 ACP.
As for and upgraded RSA, I've come to find that the stock Gen4 RSA on both the 20 and 21 work very well, even for heavy/warm 10mm and .45 Super. Compared side by side I can tell the stock RSA offers greater resistance than the aftermarket 24lb RSA I had been using.
Another issue is that a 21 is slightly lighter weight, which although small, will result in slightly higher slide velocity with warmer loads. This is likely a non issue when using "regular" .45 Super loads, but when the .45 Super is loaded to 460 Rowland levels (as in close to 40K PSI), you want every tool you can get to slow down the slide velocity and dampen recoil. The same reasons you would want to tame a 460 Rowland is why you would want to tame a warm .45 Super.
There are some online recoil calculators, never messed with them much really
180gr @ 1365 fps = 13 ft-lbs / 22 fps recoil velocity
200gr @ 1270 fps = 14 ft-lbs / 22 fps RV
"Regular .45 Super"
230gr @ 1100 fps = 14 ft-lbs / 24 fps RV
My warm .45 Super loads, come out as:
250gr @ 1275 fps = 23 ft-lbs / 30 fps RV
275gr @ 1200 fps = 23 ft-lbs / 30 fps RV
300gr @ 1150 fps = 25 ft-lbs / 31 fps RV
Here is another one
Comparing my warm 180gr 10mm at 1365 fps to a "regular" 230gr at 1100 fps in the .45 Super I get
Recoil Impulse in (lbs sec) =
1.28 (warm 10mm) vs 1.29 (Reg .45 Super)
Velocity of recoiling firearm (fps) =
23.49 (warm 10mm) vs 25.48 (Reg .45 Super)
Free recoil energy in (ft/lbs) =
14.99 (warm 10mm) vs 16.38 (Reg .45 Super)
Even the 10mm 200gr @ 1270 fps is less than the regular .45 Super.