Fire Moths are the fastest but also the most thinly armored. I’d also look at Vipers (another Bear design), Ice Ferrets (a Wolf design that appears on the General Clan MUL lists), and maybe even a Mongrel (a Shark design that presumably the Bears can buy after 3052/Tukayyid even if it doesn’t show up on their MUL lists). These are all thickly armored, low-end medium designs with above-average speed (7/11+) and jumps jets in the case of the Viper and Mongrel. Unlike Fire Moths, these taxis can stay in the fight with their battle armor after dropping them off.
Like real-life APCs and IFVs, omnimech battle armor taxis do not usually make repeat trips for multiple units of infantry. If each Elemental star does not have its own set of rides, then your first star of Elementals will be picked off without support while the taxis spend the next two turns returning and delivering the next star of Elementals. You want to be able to deliver your entire force (or the bulk of it) at once as the situation requires. Otherwise, your taxis are just a conveyor belt delivering a little bit of your force at a time to get destroyed piecemeal by the opposition’s full firepower.
Instead of another two stars of Elementals, I’d look at a star of some heavier, slower, but longer-ranged designs. The Mad Dog is the classic Bear fire support omnimech. But you could also mix in Executioners (also a Bear design), Timber Wolves (appears in the art with Bear insignia all the time), Stormcrows (design from the Bears’ allies in the Snow Ravens), and Black Hawks (old design from the Bears’ rivals in the Hell’s Horses)
Might look something like this:
Binary Supernova
Battle Star
Timber Wolf (or Executioner)
Mad Dog
Mad Dog
Mad Dog
Stormcrow (or Black Hawk)
Striker Nova
Mongrel
Elemental Point
Viper
Elemental Point
Viper
Elemental Point
Viper
Elemental Point
Ice Ferret
Elemental Point
If you want a full supernova trinary, then add another star or nova, as you see fit.
This is a balanced, flexible, mobile, survivable, hard-hitting Clan binary. It can do lots of things, but usually the Striker Nova will be in front, fixing opponents with Elementals and shorter-ranged weapons while the Battle Star provides heavier and longer-ranged firepower from further back. Other tactics include using the Battle Star’s thicker armor to fix the enemy while the Striker Nova hits from the flanks. Or using a closely grouped Battle Star to punch a hole in the enemy line for Striker Nova to exploit.
Hope this helps.