I am willing to switch from 700x23c to 700x28c (front) and 700x25c (rear)
I used a 28mm front and 25mm rear for years on a road bike where the seat stays were too tight for a 28mm on the rear.  I felt that it was the wrong way around (the "fat" tyre should be at the back) but it worked fine.  I never had any issues with control or skidding or the bike feeling unstable.

In my case I used Continental GP4000s in summer and Continental Gatorskin in (Australian) winter, but I used the same model tyre on the front and back - just different sizes.

You'll be fine.