While an interesting idea, it does have 2 downsides not mentioned so far:
- No Partial Construction - if a build order for 100 ground units reaches 50% completion when the planet is attacked, the defender has 50 units to play with. If one "100-strength" superunit is 50% complete, the defender gets nothing.
- Scale on map - scaled-up units won't require proportionately more space on the tactical map making very large (100+) scale combats less realistic. This could also result in tactical exploits like using large numbers of single-units to tie up opposing troops while having one super-unit tackle them piecemeal.
Adding the option to manage ground units in "fleets" would seem a better option for simplifying control but perhaps a better way is to implement auto-stacking where similar units are grouped together once they exceed a certain threshold (e.g. more than 20 units results in each model representing 2 units, more than 50 makes it 5, etc - such stacks having the number of units displayed alongside). This is how large numbers of units are handled in Imperium Galactica II and it keeps numbers down without imposing too many other compromises.