Im playing an Alberic campaign and just got Gotrek and Felix. They are fun, but there are some real downsides to having Gotrek as a lord rather than a hero.
The biggest is, as Bretonnia, he obviously doesn't get access to vows (nor should he). This means he pays the (very expensive) pre-vow upkeep costs for any cavalry in his army (and peasants add to the realm cap). This makes him pretty much unusable as an army lord.
I think it would have been MUCH better if he had been a hero - and then given him bonuses when fighting in an army alongside Felix. In addition to feeling less clunky, I think it would feel more lore friendly as well. I know they led armies in the books, but more often, they were soldiers fighting on the front line.
I know it's probably too late to change, but he does feel very clunky - especially in a Bretonnia campaign.