Midbass is suppose to be part of your front stage, it is localizable after all. All this arguing over what Meade did.... notice they went in front doors? Unless you really dont care if your system stages well at all, and just want pure loudness, keep the midbass in front where it belongs.
Can a 10 be run as midbass? Sure, hell there are 15" home audio 'midbass' speakers out there. But, not just any 10" subwoofer designed to reproduce subbass will also work well as a midbass driver. I'll be installing twin IDQ8's in my doors one of these days, originally sold as a 'subwoofer'... but their freq response lends them very well to midbass. Will the 10" subs you are considering run flat up to 300-400hz, in your 'small sealed enclosures'? Highly doubtfully.
If your friend wants kick *** midbass, and who doesn't, stick with 8's in the doors IB. The right drivers will reproduce up to any level you'd consider SQ still being audible.