I like the idea, and I agree with your sentiment and concerns. I think FRENS works, but I am personally in favor of an Alchemica incentive. An interesting idea was just proposed in the "A drip feed of Alchemica, and the delay of sale 3" thread regarding airdropping a pre-mine of Alchemica to realm holders based on vintage.
A similar mechanism for gotchi’s might be interesting. Maybe use the age based approach for avgotchis to determine their Alchemica airdrop.