Free unlock code or not, there is absolutely no excuse for locking female playable characters behind Patreon.
You are not "incentivizing players to show support," you are, in fact, locking basic game mechanics behind a pay wall.
The kind of thing E.A. is infamous for!
I should like to think that I don't need to explain why emulating them is a colossally stupid idea.
Try making the Patreon incentive something properly tempting instead, such as:
Extra kinky outfits and sex poses. Extended character stories / sex scenes. Silly weapons and vehicles. Extra voiceover packs. Fancy and/or silly hair styles.
And that's just off the top of my head.