*shrug* I wouldn't worry too much about overpowered.
What's the difference between a person working all day making fireball potions (where are potion rules anyhow?) or a guy working all day making explosives with skills in Chemicals, Demolition and a couple of household products... or just loading a cheap vehicle full of fuel, fertilizer and rusty nails, for that matter.
Or lacking any skill, working a simple day job and spending all his money on any kind of explosives, missiles... I'd recommend Ares Mk 27 Incendiary Bomb's. 500 nuyen for 19P fire damage (which halves armor and does continued burning damage) for only 12 avail, what's not to like?
It's not about characters having bombs, the tricky part should be getting them in place and detonated at the right time without being discovered... or getting yourself blown up. And that'll be the same regardless of how the character got the bomb.
Most runs, heavy explosives aren't really practical anyway.