no. or upgrading. sorry. it's important that we keep asking though.

Oh no, it's good that you ask. Frogboy has implied that Stardock actually pays attention to how often issues get brought up on the forums, more attention means they consider it more important to address. So here's +1 posts for ability to combine units and ability to upgrade individual units.

These two features actually go well together - the big problem with combining units is what to do if they're not exactly the same. How do you represent a group of two axemen and two daggermen, or two axemen with leather armor and two unarmored ones? This issue disappears if you can upgrade unit gear (or training - why can't I send my noob units back for veteran training after they've been created?) - if you're trying to combine several slightly different units, you can just upgrade the weaker ones to match the others first. This could even be automated as part of the combining process; you could get a popup: "Are you sure you want to combine these units? It will cost [x] additional [resource] and [y] additional [time] to upgrade individual units to match the group." Or even a full-fledged interface similar to the unit creation one, where you can both upgrade units and combine units into groups, and see what additional resource costs are incurred by various combinations of those actions.

Right now I would be happy with just combining units that are the same and just average their experience. Then the player could upgrade units to make them the same before combining. This would make programming it a lot easier.

The "big problem" doesn't exist in Dominions3 since every unit keeps its personal stats. That could be the same here: drag'n'drop to combine/divide units and get a formation bonus for teams of 4/9/16...while individual units remain the same (or we could upgrade them optionally with money, as you said).

So, yes: either the units are upgradable or they are combinable, the best being both.

Count my vote here!