Even if they were fully trained troops, how would Putin integrate them into the battle plan? Where would they fit into the command structure? Where is the transport and logistics need to supply and support them? They are 500 miles from the Ukrainian border - are they going to march on foot, or is transport available? Just getting them staged and organized would be a substantial job.
I think that’s all been solved since there’s already video of them in Ukraine.
All of your posted reservations are very easily overcome. Transportation and resupply, indeed.