[Ranylyn]

I'm in favor of making Install Main Class. But not Cracked Mirror.

I'd say the second main class skill shoud be Sync Mind. Sync Mind gives you as many skills and passives as you have Youkai. On the flip side, Cracked Mirror just... you know... gives some of the FP a summoner needs to actually summon at all. Sync Mind would reign summoner's non summoning in somewhat with "wow, look at this, 2 SP for all these skills" and encouraging people to actually... you know... SUMMON.

If Cracked Mirror were the second Main Class skill, you'd go from "people subbing it for install" to "people subbing it for Ingrain/Parraeta/Ruby Beam/Shatter Beam/ etc. And with Install AND Sync Mind limited to main class, you wouldn't see people subbing it just for the FP regen when other classes simply do it better - people might actualy summon.

EDIT: Alternatively, make a main class skill that brings summon sustain costs in line with what they used to be. Youkai themselves have been nerfed quite a bit (lower growths in some cases and almost all their skills hit for Level/2 bonus damage instead of Level bonus damage) for a still-steep FP upkeep, and I feel that this could be another way to encourage people to actually use summoners for summoning.