No, I don't. If you have brought that kind of attention upon yourself, where the hiring of snipers is necessary, then you have earned it.
Now, tell me what else the possession mage can do, besides cast spells and summon spirits? Same as other mages, pretty much, and they had to belong to a traditon that allows channelling metamagic, and had to purchase the metamagic. And still all he can do is be tough.
A street sam spends money and gets that, he doesn't need to spend any karma. Recall that you can upgrade armor to be hardened. And dog pile a lot of it on, by spending money. The mage has to bind the spirit, as well, and have a goodly number of services available. Which also costs money. Armor tends to be cheaper than binding ritual equipment. Especially the crazy stacking kind. And, again, those services can be depleted, as normal, by someone with banishing.
There is also an RP aspect that some folks are forgetting: Most spirits hate to be bound. Only the possession traditions of magic could possibly have exceptions (the Loa from voodun is an example). Long term service "beefing up" the mage may become grating on the spirit, especially if all the mage does is treat it as a meat shield. It has to be a partnership, and using any power expends a service. If any mage wants to make up a possession tradition and flat out ignores the role playing aspect of it, then slap him/her with the appropriate penalties.
I see possession as powerful, but rare. I haven't had anyone try to abuse it in my games, but then, I feel what's good for the goose is good for the gander, and my players know it. If they start abusing their power, then I have ways of dealing with it.
