Please make a simple tweak to the EXP rewards received at the end of a Ballista match:
For a level 99 Match:
30,000 exp, and give each winning member 10,000CP for the nation they are allied to.
For a level 60 Match:
15,000 exp, and give each winning member 5,000CP for the nation they are allied to.
Etc. Etc.
Scale the rewards for the various caps, while giving a clear incentive to participate at the highest level possible.
If you also desire boost the gil reward as well, to the nature of 25,000 - 35,000g (It doesn't really matter since you seem to have no problem with Chocobo blinkers anyway).
This means that every Ballista match a player could accumulate enough points to feed into other events like Voidwatch/whatever and also have a small exp/gil reward.
The real change that needs to be made is to allow a Ballista match to give a player a decent amount of Conquest points, this is a very minor change that would have positive impact by lowering the price of void dust and allowing people to enjoy content like VW further.
(I say enjoy with extreme reservation)