Wotan, look up a few posts where I lay out what the Clans had in the way of assault machines before Omnis . . .
Nicki took what he could to Strana Mechty and built the logistical base to support the proto-Clans as well as re-ordering the society. While caches that were found in the Pentagon worlds did become important, it was not just for parts- look what happened with the cache the Wolverines found. The Clans probably fielded Atlas (know Nick did), Pillagers, Emperors, Highlanders, maybe Mackie, maybe prototype Devastators, and other elite assault units during the early years. The one I always wanted fleshed out was the Storm Giant since that is what the Scylla came from, was it a SL-era mech, pre-Klondike or early prototype Clan equipment mech.
Look at the Highlander for example, 'thousands' traveled with the SLDF on the Exodus. It says that no new Highlanders have been produced in more than a century (3060) but the occasional few are upgraded from the caches. But almost 1500 Highlanders were either upgraded or new build IICs were made in the 200 years since the design debuted with the Adders having the most due to the Burrock absorption. Though many have been scrapped or destroyed, several hundred still serve in the toumans. The Crusader Wolves field a lot to offset losses from the Refusal War, opening a cache to commission several stars worth . . . which is 10-15 (maybe more) Highlander IICs or plain Highlanders they had in reserve.
Say 300, divided between the 15 Clans at that time . . . and its like 20 a Clan, though I would expect more.
So . . . honestly, the Pillager is like a mech I would expect the Jaguars to adopt or seek before Clan tech comes out . . . and perhaps the Stone Rhino was their attempt to build a Pillager IIC though it had problems that kept it from being produced as much as some players wish.