Is Diaclone part of Transformers lore? Can it be? This is kinda what I've wanted for the Human Alliance / Earths Defense Command, or any other organization. (good or bad) Humanities gaining Cybertronian tech to create transforming Mechs. Would be great way of bringing back characters like Marissa Faireborn. Could also reimagine the 2001 RID, Armada, Animated, Prime and Earthspark human characters into being part of Earths Defense Command.
What little Diaclone lore there is focuses on mechs piloted by humans fighting against invading insect aliens called Waruders. In fact the Insecticons started life as Waruder mechs in the Diaclone line.
Diaclone entered Transformers canon thanks to a few prose written by FunPub to incorporate Diaclone decos of G1 characters. Lift-ticket and Burnout were Botcon exclusive repaints specifically mentioned to be Diaclone mechs, not Cybertronians.
There's also a prose written that depicts Sunstreaker's Diaclone version in red as a Diaclone mech given a spark and sentience, and taking the name Spin-Out.
Lately Diaclone-homaging repaints in Generations have gotten the "Diaclone Universe" label on the packaging.
I don't have any original Diaclone stuff, or any of the reboot figures, nice as they look.
What I do have are the Diaclone repaints from Generations and a Dead Optimus repaint of ER Prime done up with a Diaclone Battle Convoy sticker set, and my head canon is that Diaclone is the EDF's attempt at reverse-engineering Cybertronian tech to fight the Decepticons on a more even playing field.