[lineslinger]

Yeah, it would work. As you said you just have to make sure you don't surpass the amperage rating on the switch. I would fuse each lead as well.
You do have to consider the idea of putting two contrasting functions on the same switch, in the big picture I would prefer having individual control over each function rather than "doubling up" as you are contemplating.
Drilling on more switch hole isn't that big a deal and I would think in the long run having independent control of both the fuel pump and the hydraulic valve is something you would probably end up doing anyway.
But, yeah it would work.