Bombs really don't do negligible damage at all though, if in the rights hands. They do require extremely heavy investment.
'This is available in game in ways I can think of at least.'
Timebombs require being anchored like structures to count down which precludes being thrown or hidden. Conventionally.
I don't think it's a terribly big issue because of the potential destructive power of bombs (and even if somebody makes absolutely shit bombs, they have a tendency to cause a massive effect on RP, often more than what's reflective of the actual damage they're doing to people on tile) and moreover the fact that tampering with them requires skill. I assume that the bomb maker's skill relative to the disarmers comes into play here too, so you could have very hard to deal with bombs, but I might be wrong here.
Moreover, from a roleplaying standpoint, the timebombs in game are large. They're not exactly things that could be concealed without a great deal of effort and could be stumbled upon easily in any trafficked area - such as a street - even if concealed. On the other hand, they're big enough that they'd be terribly hard to hide in a more intimate setting.
Stealth and concealment play very well with Explosives already, I don't see this interaction adding anything especially with it not fitting with the unwieldy size of current bombs in game. Not to mention that absolutely weaksauce bombers already cause a huge amount of disruption (HOLY SHIT, BOMBS) because it's pretty hard to distinguish a skilled users bomb from a shit dud without standing in the blast.
My opinions come from playing around with explosives extensively.