Based on how Furman also used the word "Maximo" in Reaching the Omega Point as part of Antagony's rank of "Herald Maximo" to denote her status as the highest of all Heralds of Shokaract, I get the sense that the "Maximo" in "Liege Maximo" was likewise not a name but a rank. The guy was also often referred to as "
the Liege Maximo", as if to refer to him by a title and rank rather than a name (as in, he was the highest of all Lieges in the Cybertronian Empire), like how Jhiaxus was known as "the Liege Centuro" (likely dervied from the Roman army commander rank of "Centurion").
Had the Marvel G2 comics been allowed to continue properly instead of wrapping up so hastily that Furman had to later write "Alignment" to give the Liege Maximo cliffhanger some degree of closure, it's possible Furman would have given the Liege Maximo a proper name in the proceeding comic stories yet to come. Or, had Furman gotten to introduce the character in the Dreamwave G1 comics before they too went under, he might have revealed his name then.
And, if Furman had gotten to flesh out more of the original mythology of the Thirteen Original Transformers in said Dreamwave comics, it would have interesting to see how they would have been handled as not being Primes at all (in contrast to how Forest Lee later declared them all to be Primes in his Fun Pub comics). The most that's known about what Furman had planned before Dreamwave went under was that the War Within: Age of Wrath comics would have revealed Grimlock (of all bots) to be a direct descendant of the Thirteen Original Transformers.
That is indeed Grimlock in a Seeker body, yes.