Did not need it. The Think Tank had no use to make any advances in Power Armour.
Power Armour was being developed and built by
Vault West Tek. The Think Tank in Big Mountain, was there to make new science and new weapons.
I don't see the need to have new types of Power Armour pop-up in DLCs.
Power Armour was also a new thing before the Great War. Early power armour were proto-types and T-45 power Armour wasn't the best. T-51b power armour came out in the last few years before the great war. There would not be many different types out there.
Advanced PA and advanced PA MKII and the crap Enclave PA in Fallout 3 were all created after the Great War by the Enclave only.