That really depends if the slowdown fix is a matter of heavy code modification or adding extra processing hardware to the cartridge itself. Apparently the slowdown problem disappears if the 68k processor is overclocked and doesn't cause problems due to the game structure. The game allegedly had a
troubled dev history, this being Minakuchi Engineering's sole Genesis developed game and all.
It would be a huge undertaking to rework the code to be optimized without breaking the already shaky code. Having something outside the base code to run the game better is more likely. The M2 port of the Sega Genesis Mini more likely has the emulation CPU for Wily Wars clocked at a higher than normal rate if what I looked up was correct. I would have to verify by testing the Genesis Mini release in BizHawk to be sure.
Edit: The slowdown is also still present in the English version of Wily Wars from the Genesis Mini when played on BizHawk. I just tested the Gemini Man fight and there was very noticeable lag when Gemini Man shot his bouncy laser on screen. This gives me proof for myself that the Genesis Mini does adjust the CPU cycles for Wily Wars since the one video showing off the reduced lag is on the
Yellow Devil fight, one of the notorious lag generating spots of the collection.
