The gentleman that introduced the idea of protomechs for IS forces hit upon a very good idea. Protomechs within the innersphere would be of great use, but certainly they'd need to be much more standardized.
I'd propose a rather simple application of tonnage, 5 tons, 10 tons, and fifteen tons would be quite acceptable enough, and fit within the standard frame of 5 ton adjustments. It would also fit fairly well within the ideal of Innersphere designs being more standardized than their clan opponents.
I propose a powerpack fitted to the back, that contains both a light fusion engine and a compact gyro.
I also propose the ideal of HFF for external armor and an internal structure composed of composite. Which gives the design greater armor potential for less, as well as makes it much more vulnerable once breached.
The suit itself would be piloted by inserting a standardized light battle suit into the frame of the mech, whereupon the head is lowered and sealed, allowing for the warrior to fight on, as well as to survive in case of catastrophic failure.
The suit itself would be more akin to a warsuit than a protomech, with small and medium lasers, MML systems, MRMs, SRMs and LRMs being common. Light auto cannons, plasma rifles, and light ppcs being fairly common, and weapon systems like the thunderbolt being fairly rare.
Such systems would necessarily be much more modular than protomechs seem to convey, with a tendency towards features such as modular weapons mounts being quite common.
Such designs would necessarily be glass cannons, with the heavier warsuits being more capable than many light mechs, but with a much more limited battlefield life span, and decreased utility within more open battlefields.
This is of course only a sketch of an idea, and not the whole of the idea itself.
