Forcing MSAA like that is difficult and not possible without breaking most games.
I explain the reasons for that in here: https://github.com/doitsujin/dxvk/issues/5075#issuecomment-3076014089
It's even more problematic with D3D11 games.
Not forcing but changing it's sample count when it's already active. Unless that's hard to do as well?
Could work in some cases but would break every single game with custom resolves, or if algorithms are involved that rely on specific sample counts or positions.
Not too interested in doing this kind of hackery inside DXVK, this is mod territory.
The option for disabling MSAA in D3D11 is useful in some games, one that comes to my mind is Metro 2033 from 2010, which in it's maximum graphics preset either forces a super ugly AA called AAA, or MSAA x4, so I usually put MSAA x4 and then disable it with the dxvk.conf option cause it takes too much performance.
But I was wondering if a middle ground could exist.. and instead of completely disabling it one could instead force it to x2 on the basis that it's already enabled in the game of course, or x8 for people who want crazy good quality.