To be honest, I see the bugs as falling into three categories;
Flesh hooks - I have no problem with flesh hooks working as offensive grenades. However, they shouldn't be handed out like candy to everyone. Lictors having them is fine, but I don't want to see them universally issued because they shouldn't be. Not every bug species uses flesh hooks.
Gaunts - Termagant or Hormagaunt, these guys don't need grenades. They just don't. I concur that not having grenades means you'll take extra casualties assaulting a defensible position, but to my mind, fair enough. These are, as someone said, meant to be "you run out of bullets before I run out of bodies". Make them a point or more cheaper - so a brood of the same cost can just ignore the casualties - rather than giving them grenade-a-likes. The best upgrade for a hormagaunt is another one behind it, and its main protection is putting another one in front of it...
Genestealers - now here (unlike the disposable bugs) I see Chuckle's point. These are supposed to be the elite, lightning-fast ninja alien killing machines of Space Hulk, and the presence of someone's waist-high herbacious border shouldn't leave them striking after necrons. Equally, whilst they could do with being cheaper, making them cheap enough to ignore the casualties dilutes their elite feel relative to the smaller bugs above, and makes them stupidly overpowered if they do actually catch someone in the open.
Genestealers should be (a) fast, (b) encouraged to stick to the shadows and ruins xenomorph stylee and (c) able to dash out of said shadows and remove your vocal chords before you can yell "contact front!". I therefore propose a nice, simple rule for them:
Genestealers ignore difficult terrain.
No difficult terrain, no reduced charge distance and no initiative 1. Problem goes away at source and you are able to move around the bits of the board which are a genestealer's natural environment as a side benefit.