Cybertron Civil War. From the G1 comics and cartoons, to the Bay movies and Prime. We are told about there being a war on Cybertron, there have even been a couple of stories told during it, but this would be a full-on version of the beginnings of the conflict between Autobots and Decepticons, before they turned up on Earth. Sort of Clone Wars styled, in terms of structure, and maybe even in execution. They manage to keep having new characters showing up all the time, and lots of variations on the core cast, something none of the 3D CGI TF toons have done yet. Plenty of opportunity to sell toys if lots of characters show up.
I'd probably open with a multi-part episode about the Autobots first big victory under Optimus Prime's leadership. Something of a take on the old comic "And there shall come...a leader!" story. There could be flashbacks and side stories focussing on one particular character or group, but it'd generally be a show about a robot civil war on an alien planet. First season would mostly be Prime establishing himself as a competent leader and challenge to Megatron, maybe introducing the concept of combiners in the finale, if we could get toys of them made.
assembling a Neo-G1/TF:TM cast. Please PM if you have (or know of) the following at a reasonable price: Classics or Henkei Prowl, Astrotrain, Ramjet, Skywarp, Sunstreaker, Sideswipe, Blurr, Perceptor, GDO Wheelie and Springer, or 3rd Party Motobot Arcee, FP Springer, iGear Ratchet and Ironhide, City Commander (and/or Ultra Magnus), Starscream (deluxe) Coronation add-on, or Spike and Daniel in their Exo-Suits.