Not to discourage you or anything, but let me warn you that making patches for new features will not be a cakewalk, and will take several days to finish. It took me 2 weeks to extend Kangaroo to 256-bit range for example.

Anyway, it looks like in this file SECP256k1.h is where all the types are defined, we need to define a "fake address type" for public keys like #define PUBKEY   3 and then we don't have to worry about adding X, Y points or making a function to calculate points because as you can see in this file those functions are already there.

I said "fake address type" because we no longer store an address prefix in PREFIX_TABLE_ITEM->prefix if PREFIX_TABLE_ITEM->sPrefix==PUBKEY (I think that's what sPrefix is for I didn't study it hard enough), we store the entire public key.

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So you're trying to use VanitySearch to find private keys that have the full specified public key, am I still following? Or just ones with the first few characters of a public key?