All right it was foolish of me to think that all future Union events will give 300 Holy Soul Points.

Needless to say, unless there is an alternative source of HSP exchange, you will only be getting 200 max HSP for all Lilim related Union event in the future.
Meaning if you've already used up all 300 HSP you got from this event to unlock Cagliostro like me, you'll be stuck in getting Shingen until another 6 more Union events.
This means, even after all 7 element Unions have completed a full rotation, you still won't have enough HSP to unlock both Morgan and Shingen.

Good news is they will seem to reprint every other element in the process as well. (I thought they only revived the Light lilim Union because the first one didn't have any weapons or lilim rewards).