I would assume that adding more units to the base game would be possible. They can add new units via commanders so I don't really see why they couldn't add more units to each faction - if they wanted to.
I think one thing that would really help out and possibly attract the attention of a lot of people that used to play, but quit, would be a big commander overhaul focusing on the commanders that come with the base game. I'm sure everyone has seen the massive thread about commander overlap being a problem so I'm not going to rehash any of that... but I do have to admit that most of the basic commanders aren't very intriguing, at least on the German side of things. They also tend to have little impact on how the game is played.
Not sure if redoing those commanders would be possible/considered by Relic but as I've said in this thread... we already have a LOT of commanders. Continuing to add more and more will eventually prove to be more of a problem than a solution.
Nail on the head there in regards to the initial commanders.
It was seriously like "Does it even matter?" which commander you selected as the game essentially played out the same irrespective of choice - which was a big criticism at that time.
Then the next round of "Pay to Play" commanders showed up...and now you have the conundrum we're in now.
Original commanders were too dull and non impacting of game play - then you had the pay-wall commanders that offered a lot more variety (and I use that word loosely as most would say OP) yet you had to PAY even more to use them, no if, buts or maybes.
Inverse is great to watch and his opinion is smack on. Even the option of making commanders "earn-able" won't help the significant other problems this game faces - but it's at least a start.