I am regularly asked about an argon (Ar) inflation system for trimix classes, here are some thoughts. Assuming that the class is not held in cold water, but rather somewhat more temperate, then with the early mixes on the DSAT Trimix class (about 20% He) then you can get away without an Ar inflation system, as the He% increases however (and on the deep dives of the class, students will be diving 16%O2, 50%He down to a max of 245') then a separate system for drysuit inflation becomes all the more useful. That said, Ar is not necessary, air will certainly suffice in a separate system. If the waters are colder however, then a separate system might be advisable right from the first dive- He certainly chills you down.
Remember, this information is NO SUBSTITUTE for proper training- attempting to perform technical diving without proper training or equipment may result in serious injury or death.