If the Premier League title was mathematically wrapped up by late march/april..?

Yes

I'd rest players. Invincibility would be nice, but it's just a bonus. The champions league is much much more than that.

I'd like to see Alisson up front, but that might just be me...

Yep, with the odd youth player coming on every now and then or getting a start

I think it is and it would be important just to focus on the next game.

Definitely more focus on champions league