I know this is a long shot LOL, but I would love to see three additional warlock patrons added to the list. These would be based on the generic ones. If you chose one of these, similar to the oath breaker, you can multiclass, but you can't change their class. There should be a way to get out of the contact but it shouldn't be cheap (I would suggest 2500 gold per current level, better start saving up), this way you can respec your character if you want. Or the contract can be set like a tag (IE one eyed) so even if you do respec, you are still under your old terms for the rest of the game. Hopefully extra dialogs shouldn't be that big of an issue, even text based using some of the existing dialog (repurposed) would be fine. I would add a warning to the description that this could effect the final outcome of your gameplay, you have been warned. The rest of the contract terms and the final result should be left blank and up to your head cannon.
Auntie Ethel:
When you meet her in the Grove, you know who she is immediately. "High Sweetness, how's my little Petal doing" then go into tadpole dialog. You will get the fay stats/perks; however, you must let her do as she pleases
with her young plump ladies
. You will still have to pay the price for her "help". Break the contract in any way, game over and you live out the rest of you days as a frog maybe even a mindflayer frog, lol. You may also freely visit her underground lair? Just don't touch her play things!
Raphael:
When you meet him and he sends you to the house of hope, you simply remember being there before. Later you must agree to help him
. You get the fiend stats/perks. If you break contract, well you die and get to be a Lemur in the Hells (game over). Make it to the end of the game and
? Well your epilogue will be a bit different lol.
Harleep:
When you meet him, you have already offered him your body as part of the contract (thus through out the game you will have the umm moments with companion comments), so he will just require a moment of your umm time at the House of Hope. He would care less what you do to Raphael (same as now). Same stats/perks as a fiend patron. If you kill/attack him he will take your mind as well (Enjoy the Blood War)... as per your contract...
These wouldn't have to be major components or plot points, just role play points that give you the feel of having to meet your end of the contact just like Wyll does. I cant think of any other beings in the game that could offer a contract or even a vague one like tapping into a Great Old One's Power. Maybe you could become a warlock of the Nether Brain as a "Great Old One" option. That would have interesting outcomes when you find out. The option would be (Mystery Patron).
And as always, you still can chose the other patrons. This could also make an interesting mod, for those with the talent.