Or it only affects droids costing 3 pts or less; the only piece other than mice that would be affected is a BD in a Gha squad....
...Really, though, I'm not sure it's
mice that are the problem. If we work in a mouse-activator, then people will go back to Ugs and Rodians; I think what would be more helpful is a "Fodder Activator" piece, which activates all enemy characters costing 4 pts or less within 12 squares....
...But then people would learn to keep their empty fodder activation pieces at the back, and the only thing we'd gain is the removal of mouse-walls.
Instead, I think that something like the Mando CIO
as a Fringe piece would do the trick. Cost it at 14/15 (to allow for Ugs/Mice or Caamasi/Salacious), make sure it can survive a gallop or strafe (ie, 50 hp). Having this piece available through the often-used Lobot would give every tempo control squad a reason to second-guess its strategy. So often, people use Lobot to bring in 6 activations (or 10 if they have Gha), and that's simply for activation help. I think the fringe CIO would do the job even better when you're against Rebels/NR/Seps/Imps. And when you're not against those factions, then you can bring in whatever you normally would. As always, the faction-specific version (ie, Mando CIO) should be cheaper and better, but I think the CE is so useful that it should be available to all factions.
Edit: There are other ways to make the piece survivable too:
-Give it Diplomat and 10/20 hp, so that you need to be careful with it, but it won't get killed on the Gallop/Strafe/Barrage attacks.
-If it has Diplomat, possibly make the CE require LOS to an enemy. This would likely make the piece ineffective, because against many tempo control squads, you can't get LOS to their pieces until after the first big strike; playtesting would need to bear it out.