I agree, there needs to be some top of the line rewards to give people reason to do support fates.

Should drop 3 to 5 frags with a chance at seals or cloths. That way, if you do enough HELPING BA RUNS fates you can slowly upgrade your gear to the point where you feel more comfy trying it. That's basically what people are doing with frag farm runs, do the easy stuff so that you're better geared for the hard stuff.

Should also have a chance at a realy good ba minion. Maybe a minion ozma to go with the mount. That way people can say "hey, I think I'll just chill outside and help ... Cause I want that minion!" Or "oh, a discord claimed this instance? Cool, we get that support fate now".

Should also give 20 crystals cause its super annoying.

So yeah, tldr ...
It should give you frags for slow but reliable gear progression, it should give more crystals because of it's difficulty and it should give a small chance at seals and an exclusive minion to encourage people to do it regardless of their interest in helping runners.

The way ba is designed ... Before it dies its either gonna became truly epic pvp driven by salt or completely run by discords ability to muster up enough people to control an instance fully.