With FE7 out on Switch now, I decided to make a calculator that can generate the most supports possible. You can also ignore characters that you won't get, like Harken/Karel choice or those not in the Lord's route you are on. I also made an option to force a specific pairing if you wanted that ending, like Marcus Merlinus or Rebecca Lowen.

You can find it here: https://pastebin.com/5JPqDNER You can run it online here: https://www.tutorialspoint.com/execute_python3_online.php

Just copy and paste into the left side.

The characters to ignore list is near the top, you can see the ["Wallace", "Farina", "Karel", "Karla"]

And if you want to force pairings you can find that a little further down:

specific_pairings = [ (("Pent", "Louise"), 3), (("Marcus", "Merlinus"), 3), (("Lowen", "Rebecca"), 3) # Add more specific pairings as needed ]

It should be pretty obvious how to adjust those two conditions.