The idea of the Terrans could be reused to introduce more obscure characters from Transformers: Generation 2 and account for new toys by making them born on Earth instead of traveling from remote battlefields.
Earthspark suffered a lot in writing, especially after Season 1, but the concept of the Terrans has potential. Especially since it is a good\* way to account for some characters (new toys) by making them be born on Earth rather than travelling all the way from some remote battlefield. And also, the concept of the Terrans could be also be reused to reintroduce some of the more obscure characters like those from Transformers: Generation 2. Not to mention the idea of the Autobots and Decepticons starting to run out of natural born Cybertronians and subsituting Terrans to bolster their ranks back on Earth. \*Call it lazy but some brilliant moments in writing were born out of laziness. For example, the idea of Leia being Luke's sister.