how to make even bigger units?

[O'ETAIPOS]

As you expressed a desire to keep your current campaign alive, I thought I should mention that if you do change the unit numbers, you will have to start a new campaign.

I'm not sure, I think I changed units quite a few times mid-campagin (but those were mainly ownerships and attack/defence). I think that current units will need retraining, as they will not become bigger automaticaly.