To the first half of your idea, do we really need an expanded explosives system to suck up CPU cycles every time an explosion goes off?
To suck up so many CPU cycles we need extremaly big explosion like one made by missile silo. Otherwise the system will make explosives more useful and dangerous both for zombies and player.
Digging many pits with explosive! Or even more - burn a house, place a bomb in center of the house, explode near gas station and it attracts many zombies to the street, the bomb ticks off, nails is thrown and spread over all street, kills many zombies... there'll be new tactics, new ways to die... die stupidly.
About chemistry. The compound reagents it’s just beginning of new advanced chemistry system which pretended to be more interesting than now. Unknown substances and some… “playing” with them. I don’t think if you get a bottle with some liquid you’ll immediately know what’s that liquid unless it’s written on the bottle or it’s become known after you tried to mix that with some known reagents. Something like that.
You have a bottle of sulphuric acid (H2SO4), and a bottle with unknown liquid (it’s lye powder, KOH)
And you tried to mix them, so: H2SO4 + 2KOH => H2O + K2SO4, and player gets message: “Nothing happened”.
But if the player tries to heat up the mix he will get message: “It gives white powder”
I don’t think you need to hear that it will make chemistry more changelling and interesting.