A (very) rough estimate for the price return of removing the gun and some sensors would be four, maybe five tokens. The parts're probably more expensive than that, but packages are cheaper than their parts--the gunnerbot is a package. Also, you're adding stuff, which is probably a token, so I doubt you can get it cheaper than four tokens. It's still a large wetware robot, after all.
On normal missions, I think the only valuable use would be for retrival of corpses from dangerous situations. The problem is, it's not going to be particularly useful most of the time; Here's a list of requirements:
--The danger must not be passing (a firefight will be won), or the corpse must have a risk of being targeted prematurely.
--No armored allies can be present to retrieve the corpse. I don't think this is gonna impact a fight much by removing a combatant.
--The gurney bot must succeed in the retrieval, not being shot or damaged before safely returning the person.
And here's a pair of problems:
--I don't think Gunner bots are armored, and gurney bots can be targeted early, before they're even used. It has to survive the mission leading up to its use.
--It is wetware, and therefore vulnerable to mindfuck. This could mean it's damaged before being useful, like the above, or it could attack a teammate.
It would be valuable for cases like China-9, where people were trapped near ground zero, and players had to rush back in to rescue them; I think Nik fell to this fate? However, most of the time, we don't have sitations like that. Four tokens (or even three) is a bit of an investment for something which has a decent chance of not being useful on a mission.
That said, sure, it's a decent thing to have available, for BLOPS and such. I just don't think it should be in the armory, because someone will waste money on it. We already have too much armory bloat.