So, Periphery Factions Can't Build 'Mechs, Or Tanks, Or ASF In An ISaW Game.

[SCC]

Was just reading through the research rules in 2SW when I realized this, Periphery Factions start out with a BattleTech rating of 2, which limits them to Tech Rating C units, and these there unit types, weather to to structural or engine tech ratings all have a minimum Tech Rating of D.

[Alexander Knight]

A lot of interpretation from each group here.  On the one hand, the Periphery continued to build standard Tech D units throughout the Succession Wars so you could say yes.
On the other hand, Periphery armies are notoriously more ramshackle.  One way to handle it would be to downgrade either the armor (by 2) or the damage values (by 1 in all three categories) of each new Periphery unit.  This would represent the downgrade to "primitive" machines.