I like multiplayer, but I hate imbalance. I hate the feeling that I won because my base units were just better. Or the game was decided before it started because I picked the right units by chance and from that point on it's an unfun one sided battle. The Elite Unit thing seems like maybe a good idea, in singleplayer.
Really it will be horrible for multiplayer balance and ruin lots of the competitive aspects. Especially if there's any pay to win microtransations associated like with CoH2's generals. Or if they make you grind through multiplayer battles to unlock things, putting newer players at an unfair dissadvantage.
So either make the units same stat versions of units already in the game, as pure aesthetics choices, or just give all players all playable unit unlocks from the start. Another option is allowing people to switch up unit choices and adapt to scenarios strategically (which should be part of a strategy game after all) though only allowing a maximum of 3 at any time. Or just have a "no elite units" option for people who want a more balanced playing field.