Thanks for the feedback. Actually, ESF makes quite a lot of changes to the Companions but there is, in reality, very little crossover with it. They both add the "Animal Pelt Collection" quest, although, ESF has a slight bug where the pelt required spawns in Jorrvaskr. With a minor edit, the two Mods are actually compatibile. I also thought that, given the charcterisation of the twins, it was unreasonable that Farkas would ask to be cured in the "Purity" quest before his brother had taken the plunge, but that he would ask to follow suit as soon as possible afterwards.
I did want to keep it as simple as possible in light of ESF and also not duplicate the effort. I wanted to stay as true to the vanilla game as possible and so tried to make the changes as unintrusive as possible too, the "Animal Pelt Collection" quest, just seemed too obvious to not include as most of it is already coded and it can slip in seemlessly with minimum fuss and the twin issue, to my mind, breaks immersion somewhat as Farkas follows his brother's lead in all things. I also made sure to carry over the changes from USkP for compatibility.