Yeah, the biggest gripe people have about the MMP and the MME are the form factor while they're running in the field, but it doesn't bother me all that much. I just carry mine in the Petrol and it fits perfectly in a stored position. However, during the show, it's kinda awkwardly standing so that half of the preamp is sitting out the top of the bag. If you're worried about your gear getting spilled upon, there's no protection.
The only thing I thought of that might work for the MMP is the backpack bag that has the shelves that kinda fold down at a 45 degree angle when the bag is sitting on the ground. That might work pretty good.