From experience, most Size 1 units are Scouts, Strikers, and Ambushers... so if you want to make a Light Command Lance, would you consider picking up a single Medium element? (your own research will net you far more for yourself than I can guess, but here's a brief list from a quick glance for an example):
Juggernaut - Centurion, Hunchback
Sniper - Clint, BlackJack, Griffin, Shadow Hawk
Missile Boat - Whitworth, Dervish, Trebuchet
Skirmisher - pretty much everything above and then some
Some of these actually overlap roles based on the variant, and most I glanced at appeared to be "InnerSphere General" which should give you the flexibility to be considered a DCMS formation, but thats up to you and your end.
A single Medium with 3 Light units should still be considered a Light Lance, and therefore still meet your criteria (Light, Command)