That'll decrease the possibility of people using JACS, wouldn't it? The project here is JACS, not solely the vpn itself, I imagine the goal here is to encourage the usage of their native token --namely JACS-- on their services, not XMR or DOGE.
True that more payment option will attract more people, but I can't see how it'll boost token usage, and definitely can't see how it'll benefiting the investors.
I think it's okay to place other coins like aprilnot said, as long as there is something different when they pay using JACS tokens, it will not reduce token users because people are sure to keep choosing something which is more profitable