If a full remake as originally proposed is going to suck up too many CPU cycles, why not settle for a couple of tweaks?
1 - Greatly increased noise. Explosions should be horribly loud, and using a grenade in the middle of a city should be as risky a decision as blasting away at stuff with a shotgun.
2 - A “blast radius” and a “concussion radius”. A zone that actually deals damage, with an outer zone that only stuns. Perhaps a standard grenade has a flashbang “embedded” in it. That is to say, a grenade will have the stunning effect of the flashbang, but with the 3x3 blast at the center. This would make it so that even enemies not hit by any shrapnel aren’t totally unfazed by a grenade exploding a few meters away.
Side note - I’m all for more craftable explosives (beyond pipe bomb, grenade, mininuke), but leave the chemistry out of it.