Don't think so, but the new guard formations aren't cadian exclusive. Only the detachment and the relics are if
iirc.
Emperoes shield formation could be nice to get move through cover as a fluffy bit of catachans.
Wyvern is a good shout, fits well with the theme as well. Catachans are most likely to use close range fire support and the wyvern would do a good
nib of shredding through jungle canopies.
More boots on the ground can never hurt too much either. You ideally want to stay away from the more heavy duty tanks, but hellhounds are a favourite of the catachans (say hello to Mr yellow). Getting a second box of heavy weapons so you can have a full lascannon and a full heavy bolter would be useful when doing it platoon style.
I would recommend doing one platoon as an addition to your
CAD, running it as the formation if desired . Then your vets become your special weapon delivery system, (shotguns on a few of them for close encounters).
Possibly get the defence force if it's within your budget and then swap the leman russ out for something more catachan, like a wyvern