Huh, that's something I never knew, I thought the PCE was capable of displaying 16 32px wide sprites on the same scanline...
Do you happen to know if other systems of the time also had this limitation? Like say, the Game Boy or the Mega Drive?
Nope, a 32-wide wide sprite counts as 2x16 pixel sprites on the PCE.
It's roughly the same "one screen width" pixels-per line graphics-processing limit on all of the 4th-generation machines.; i.e. the SNES loads 34 8x8 sprites (270 pixels), and the MegaDrive loads up to 20 16-wide sprites (320 pixels).
That's why your wish for Flame Zapper Kotsujin just isn't practically-achievable. It's also why the SuperGrafx is such a powerhouse for it's time.
It's not the dual backgrounds, since the other machines had those.
It's because it could display 32 sprites (512 pixels) per-line when no other 4th-gen home game-console could.
Note: I'm deliberately leaving out both the Neo Geo since it was expensive Arcade hardware, and also the X68000 since it was an expensive Home Computer ... and I'm biased!!!