I must disagree with your impressions. Maybe level 1-7 have the starting mercs and or rotation mercs, but 7-15 usually have other mercs.
The issue is as well, that rotations are there to show people how some mercs feel and of course people are going to try them out.
Also, just because someone is playing a merc on rotation doesn’t mean they don’t own that merc.
And although I agree with the premise that more varied mercs on the battlefield would be welcome, I just feel that many people under level 12 or so are not ready to play some of the mercs out there.
Redeye, Phantom, Sparks are just a few example of very specific type of gameplay that needs to be learned over some extended play-time and merc learning cannot be disturbed by lack of knowledge consisting the maps, game mechanics, objectives, etc…
A few days ago I saw a level 6 Skyhammer who was standing next to an ammo cache to get ammo back… Just saying that before wishing for more variety I think we should wish for people to learn how to play the mercs they do own. Then we can think about introducing them to other mercs.
In my humble opinion I even believe that one should unlock the right to buy other mercs, a little like Star Conflict did with ships. Imagine a “merc tree” with 4 branches: medic, engineer, assault and recon. If looking at the medic tree, lets say you would have to play Aura and do X amount of support XP + 100 revives to be able to buy Sawbonez. Then to be able to buy Phoenix, you’d have to do the same with Sawbonez and to unlock Sparks, you would have to do some Phoenix dedicated medic stuff and some X amount of headshots with Vassili and X amount of caombat XP.
You catch my drift. By doing a properly designed tree with the most high skill cap mercs at the end, you would ensure people would be able to work them out. But since we’re kinda set in the current setting and that paying for mercs with real money would also bypass the sytem, it will just stay a though and nothing more.
Anyway, to sum up:
-More varied mercs = good
-More knowledge of the mercs that player own = better