Personally, I don't think laser, plasma, or waterjet are good choices for most FRC teams.
Plasma is generally sloppy, and is really designed for rough-cutting steel, not precision-cutting aluminum. For instance, if you want actually good holes, you're going to want to cut them undersize, and drill them out after
Laser and waterjet are both quite expensive. And not just the machines, the operating costs can really, really stack up.
Now, if you have a sponsor who can do laser or waterjet for you, that's a different story (Though I would rather have students do things in house, so they learn how to do it).
We're looking at building a CNC router for our sheet metal needs. They're much cheaper than the others, have more than enough accuracy for FRC purposes, can handle thicker parts without the messy kerf of plasma or water (just take more passes). And, you can do 2.5D parts, with pockets, counterbores, champfers, engraving, etc. And it will be a good holdover until you can get a nice CNC mill.
And you can build one yourself.
This fella on youtube has a lot of great videos on homebuilding routers. However, if you want it to end up being accurate and rigid, you'll probably want a significant amount of mentor involvement (Many parts of it will not tolerate standard FRC-robot-level corner cutting
)