This needs to be added, but we're obviously a bit short on buttons.
1. I can add "use_jetpack" and "use_canister" commands, but those obviously only work if you use custom binds.
2. I can make it so the "saber attack style" button dispenses canisters, but that's kind of hacky and not really clean. You can have a lightsaber and ammo dispenser, etc
3. IMO the best solution, jetpack activates/deactivates with double jump, and +use operates normally. This is the most foolproof method, but it would require people to get used to pressing it.
I'd like to do both #1 and #3, please let me know if you have a better idea.
It's an enormous amount of work to add weapons, items, or force into jka and might even require people to have a client mod just to play on the server. I've told you this before.