This is really interesting... The way you send your units has the potential for tactical movement but you really need to time it correctly... I tried a few times to flank an attacking unit and was really impressed... And then it got too hectic and I lost...
If you think that you will keep on developing it (and you should in my opinion) think of presenting the units as a single shape of varying size (depending on the number of ships)... It would make things more clear visually...