Use a 3-gang box for 2 switches and feed to outlet - to have more space to play - ok
Yes, you can do that. So you'll replace the two gang with a three gang box and just have two switches in the box. The new three gang box must be installed correctly, flush with the outer wall surface, with the hole big enough for all three gangs.

Remember to shut off all the power when doing any of this work. Take pictures and mark the wires before you disconnect any of them which you'll have to do for the box change out.

You'll probably need a cover similar to the one below when you're finished. Good luck.