If the MLO is a load side panel in the same building, there is no issue with the disconnect. This is only a 225 issue.
If you think the AHJ will buy the idea that there are only 6 breakers in a 20 slot panel and that is all there will ever be, go for it. Worst case is you are going to have to install a back fed main breaker with a clip. Say that is your plan if they ever decide to upgrade.
I've settled for a 100 amp. 24 circuit main breaker panel for the first building ( smallest one that's seems available in my area, without ordering), even though it is a little "over kill",and a 6/12 circuit "main lug" panel for the 2nd bldg. The 2nd bldg. is smaller than the first (approx. 8x10). The first bldg. is probably 10x12. Customer accepted my price, now comes the fun part Actual work. Though sometimes I think it's easier than figuring up the job (lots of headaches).
Actual work. Though sometimes I think it's easier than figuring up the job
