I can't believe I just saw this!
I am actually working on doing something like this but working with the BA creation rules in the Tech Manual to make primitive "Combat Armor". My head canon is that the relative peace of the Periphery during the Succession Wars, and the utter destruction of their industrial base and economies at the hands of the Star League led to parallel evolution with the Clan Elemental development.
Lore I have created so far:
Under Protector Arantino, after decades of corruption, a pointless war and almost empty treasury, the TDF was in need of refitting and new equipment, but didn't have the budget to go whole hog into BattleMech procurement. Focusing on external sales to House Liao and House Kurita, money was coming in but the Taurian government was just finding itself on secure footing as is - not with expanding the TDF or even replacing losses from the Taurian/Magistracy conflict. As a result, economic recovery was lagging as Taurus' defense industry struggled to sell enough material to make up for domestic losses.
This was not an ideal situation, and a solution had to be found. Enter Pinard Protectorates Limited. While known for manufacturing the Marauder, they were the hardest hit by the economic crisis currently hitting the TDF. Desperate to find something that was A) low cost; B) exciting; C) quickly able to be produced they first started studying "bug mechs" looking to procure licensing and equipment to build Locusts or Stingers. However, the costs - again - were astronomical. That was when an unexpected conversation between an engineer at PPL and Pinard-Dicolais Electronics changed everything. The PDE engineer was discussing the issues with a new commercial communications satellite they were building. A set of communications equipment and sensors had been placed into a 2 meter long frame. However, the customer was looking to have these service deep space mining stations, and as a result solar panels were not sufficient. They had managed to make the system work using a 21st century idea: RPS - Radioisotope Power Systems - a nuclear battery, but were looking to cut wait for repositioning dishes. Off hand, the PPL engineer recommending using myomer bundles, as they would allow the system excellent control and could use the RPS as a power system. To demonstrate he drew some arms and legs on the blueprints as a somewhat joke but then realized that it might actually work.
Using easy to manufacture armor from the Age of War, and focusing on upgrading mining exoskeletons, the two engineers were able to develop a basic combat armor suit. PPL and PDE worked closely together to build on the basic ideas demonstrated by the two engineers, now called "Project Phalanx". By 2845, the first combat ready suit - now called Combat Armor - was the CA-45 Spearhead. It was a 1 ton, lightly armored suit primarily equipped with a machine gun. Variants developed would include better sealing (45a), better electronics (45b), jump jets (45c), and better armoring (45d). More suits would be released as well, such as the CA55 Dagger, and the CA60 Shield. After the discovery of the Grey Death Memory Core, additional upgrade approaches were considered incorporating stealth to all suit models, and also more advanced armor types.
Game Rules for Combat Armor (Primitive Battle Armor)
I increased chassis weight by 25%, Max MP is 1 for medium, heavy and assault suits. Extra MP costs more too. Armor costs 10% more weight per point. However, costs are way cheaper. Calculate cost normally, then deduct 40%. Nothing to fancy, but I like the idea of a primitive form of BA running around before the Clans show up, AND I think it makes sense given the pressure that the TC was under at the time. It's a natural evolution.