I don't think incentivizing the offensive use of GV's is going to help a great deal with the perk GV issue, which is what started this whole thread. Honestly, if a perk GV spawns in to attack a base, its a guaranteed death for him unless things go perfectly (rare). The only advantage to using a perk GV offensivly, is that once you spawn up, theres no quick way to get out, so people are going to USE them.
Personally I feel we should both incentivize the offensive use of GV's, and reduce the penalty for using it as intended (that is, when things are tough and you need some mussle up there at the front).
Really, counting the threat from aircraft, the Panther isn't worth the 20 perks when you're attacking. The Firefly isn't worth its 15 or so, the Tiger I isn't worth the 30 perks when on the offensive. And the Tiger II certinally isn't worth 200. When you look at things overall, the perk price best reflects their value when on the defensive. In other words, when you have time to find a good possition that offers both cover and a wide field of fire, and are almost guaranteed some flank protection.