In many ways, I think the BBC-based lineup seems a bit forced, especially when Cris has lost a step (albeit also sharpened his pure goalscoring), Bale has a case of the Coentraos, and Benz has been off.
In the midfield, I'm torn on Modric, as he might be my favorite player to watch when he is on, but this year he's seemed perhaps a bit tired. If he & Kroos are both on, I think we have the best possession midfield in the world, and that also helps cover for a potential lack of an enforcer if we swapped Kova for Casemiro. I do think Kova is being groomed as Luka's replacement, and as you said, the combo of dribbling and defense could let him overtake Casemiro when we aren't facing a team with a loaded offense.
IMO, Isco's performance should make him a lock, and like you, I wouldn't mind selling Bale and/or Benz - both have done good things for us, but if they are currently hurt or off-form, sticking to the BBC only hinders the development of our young guys. I think the Asensio/Vasquez-James-Ronaldo trio has a nice blend of defensive cover, creativity, and scoring, and having Bale as a change of pace against a tired defense or Benz/Morata if we need a hold-up man is a pretty dang nice luxury to have.