Roughly as title, elaboration to follow:
TLDR: vendetta, 20-40 guardsmen, chimera, leman russ; can I successfully use some or all of that as allies for the marines in my shiny new codex, or should I leave them to their own devices, and seek answers to
AA and cheap scoring within the marines codex itself? I have one storm talon, no new
AA tanks.
Right, so back in 5th ed I picked up some guardsmen for kicks. I had a chimera laying around and ended up with a valkyrie (with enough lascannons in the bitz box to make a vendetta) and a leman russ as well. The sponsons are gone, but I should be able to manage any turret.
I picked up a batch of Mantics corporation marines to serve as not-guardsmen after I cannibalized my minimal cadian contingent to do scout conversions. This leaves me with the means to run at least a couple of vet squads, or possibly a minimum sized platoon, with
CCS (or a commisar/primaris, if that's preferable) to go with my guard vehicles (and if someone doesn't like "not-guardsmen", I'll just find another game I guess

).
My marine contingent has a storm talon, and a smattering of most of the other available units save for the newest releases. My question is: should I bring in the allied guard to support my marines since a storm talon is not enough
AA by itself, or is there some issue with doing so. As in; the guard I have aren't a good mix for allies, or I'd be much better served by just picking up the new
AA tanks and allying in a second chapter of marines etc.
I haven't nailed down a specific chapter tactics, and
tbh, my DIY will probably flop tactics regularly for fun and variety. So what I'm asking is more related to can the guard I've listed be effective allies for the marines in the current state of the game, or should I not bother to paint up their vehicles and seek answers within the marine codex itself.
Thanks for reading, looking forward to trying some of new/better units out, but would hate to leave my mostly painted guard on the shelf if they can still be useful