[Festin]

Well, I'm all for Ryujin getting a priest level (while I must admit that I never used them in MP myself, because I never managed to actually enter the sea). At least, it will give a player some additional reason to invest in an Earth bless, which is badly needed by several thugs. Too bad that E and N are two paths nicely covered by Jomon's mages.

Now, regarding the summons:
Kappa: raise the price (but not the research level), and make the Kappa Chief come with some Kappa troops. Wow, we can actually use them to enter water now.

Ujigami/Kenzoku: these are very nice as they are, so they hardly need a real boost. Their real problem is fatigue, caused by the horribly, unrealistically heavy samurai armor, which has long been in need of some weight reduction, by the way. If Jomon's mages were sacred it would not be such a problem (because an E bless would be an obvious choice), but they are not sacred and will never be, because it is not thematic. Also, Kenzoku could use a priest level like Ujigami, but it is not crucial.

Ghost General: they are almost perfect thugs, but oh well. Maybe, maybe one day we will see a death random on a Jomon mage. I want to believe.

Various tengu: never saw them summoned. Probably they could use a slight cost reduction.

Tatsu: currently useless. Increase stats and/or add H1, and/or reduce gems cost and then maybe it will become a viable choice as a flying raider.

Kitsune: eh, maybe a cost reduction? Never saw a single one of them used.
EDIT: give them Seduction, and they will become a nice and thematic unit.

Dai Oni: please make them cheaper. I am sick of Tartarians. I want to see cool national SCs like Dai Oni. Yes, I know Jomon has no way to summon them.