OBT Forum

Most Heavy Assault regiments were in the divisions it's hard to pin one down.

Not quite what you're looking for but:
10th Heavy Assault was destroyed at some point in the campaign against Amaris
11th Royal Heavy Assault survived Terra and then joined the Federated Commonwealth
12th Royal Heavy Assault survived Terra and then joined the Lyran Commonwealth
23rd Heavy Assault survived Terra and then joined the Lyran Commonwealth
52nd Heavy Assault survived Terra and then joined the Draconis Combine
91st Heavy Assault survived Terra and then joined the Federated Commonwealth
105th Heavy Assault was destroyed at some point in the campaign against Amaris
189th Heavy Assault was in the Exodus
205th Heavy Assault survived Terra and then joined the Lyran Commonwealth
287th Heavy Assault was in the Exodus

Or would a Dragoon regiment (same weight class but with conventional support) do?
35th Dragoons survived Terra but defected to an unspecified periphery state
267th Dragoons survived Terra with heavy losses and were disbanded
359th Dragoons survived Terra but were then disbanded

After thinking about it, I am looking for at least 4 disbanded Heavy-Assault 'Mechs units that took part in the campaign to liberate Terra.
And they shouldn't be Royal.

I will have to look more closely at the TOE.