I would just like a loose concept of formation. That is, try to move together, and try at best to keep the non-fighting and unit at the back. I don't think "shape" formation are needed.
In terms of having the right units where you want them. It gets problematic with support units like stealth, where you don't want any slip in the coverage.
The only time formations are really going to matter is if you want tough units to bear the brunt of an initial attack, or you want certain units to be protected. So here's an idea, though I have no idea how easy this would be to implement. Have an option for units that allows you to choose standard, formation, wall or guard. In standard, all your units go to the target area as quickly as possible. This would be the default. Formation, your units stay at the same pace as one another but don't move where they're going in any particular order. Wall will have your units with the most HP moving first, and all other units falling in behind them. Finally in Guard, units will move, keeping together with the weakest units in the centre. I don't think that keeping everyone in neat little groups is really needed or that practical from what I understand of the flow field tech, but those four options, at least in my opinion, will let you control the really important bits and at least for me answer why I would like a formation move command in the first place. Again, just an opinion, have a nice night folks.
What you really want is tank units front, long range glass cannons back, aoe support units even spread
There should be a few unit formations available, would make the battles a bit more interesting. If you group different kinds of units you have a set number of formations but if you group just one kind then you have more specific formations suitable for that kind of unit.
This I think is important. In TA I avoid using radar jamming units, because all other units don't stay within their limits. I have tried to use "guard" before to keep them close, but that never works either. Maybe if there was a way to make units assigned to stay within the range of the radar jammer, that would be good. I like the suggestion above about "Wall" and other commands too. I also still wish Uber would say something about this...
Supreme commander has the option to move units with the slowest unit's speed from the selected units. I do believe that solves the problem with moving in proper formation