You should play the campaign with the retail version, it's easy to switch between. Many models are replaced in Elite (like the Techmarine's head) so they won't show up in the campaign, and there might be other issues.
Not a problem, i'm fine playing the campaign with that techmarine, i loved the Elite mod for the models, so thank you for making this great mod.
But somehow i wished there was a Sister Of Battle Faction here which is possible to make a model using the Banshee's shoulder plates and Inquisitor's Armor, i might try to make a model of it if i got time learning how to make models.