Don't add units just to have more units. Everything should have a function or reason to exist. Otherwise you'll just be adding units that will never be used, thus wasting both your time and the player's. Every unit in the faction (and every faction in the tech) has to be loaded - even if nobody ever even sees it (unless your players run in GAE, perhaps).
in the end they all will have a purpose... i plan to make this mod huge, each new unit stronger then the last making sure that all of them are used... also i plan to make a new map that will fit this new mod...
i want it to be something like this if your confussed...
1st summoning ability, worker units, weak fighters, no range...
2nd ability, stronger units, faster building speeds
3rd, stronger units, almost instant weak unit productions, defence buildings can be built
4th, flying units, weak units obsolete, strong defences built and ready
5th, super strong units, strong enough to penatrate even the tightest defences (dragon, some form of robotic warrior, ETC)
6th, almost no resources left, dozens of buildings, lots of defences scattered and destoyed, soon to end fight
7th, final stage, whatever team makes it here first wins almost automatically, unit can attack high distances, epic damages, extremely high life, strongest armour, but high resource cost... next to impossible to summon so fight should be over by stage 4 anyway...