I've used Gregor!Severa on my main save, mainly for the red-hair o3o. While Gregor is probably not the best father for Severa, he's certainly not bad at all when you think about it, I mean his mods are consistent and she gets Troubadour and Myrmidon. Overall its okay, though Lon'qu, Vaike, Ricken, and Stahl are much better.