It's silly because he's never played the position in his life. He doesnt 'have to' be in first grade this year at all, he can bide his time because he sits behind Dufty, Widdop and Mann for his natural position (the first two are signed long term) and if he doesnt like it and wants to pack his bags, cool. He's not a Jack Bird being held out of first grade by Dylan Farrel and Dane Nielson, we have genuinely better options in the positions he suits.
I'm not sure what point you are trying to make about his size - despite putting on 8-10kgs in an unnatural amount of time, he is still very undersized for a first grader, especially centre. His defence is suspect and this would be exposed even further when he has to make defensive decisions between opposing fullbacks/centres and adjust quickly. His attacking prowess would be very limited as he wont get anywhere near the space he'd be getting at fullback or 5/8, plus it would nullify his best asset (broken field running). And the ability to make snap decisions between running/stepping/passing at the speed of first grade doesnt come naturally to someone who is used to having time on their side to make choices.
So overall, silly suggestion. We have a serviceable centre pairing in Lafai and Mann, with good young backups in Lomax and Herbert (and Aitken, if people still count him there) and he is behind all of them in the centre stocks. Probably McDonald too.
If his form in reserve grade dictates that he is a better option that Dufty or Widdop, or if they get injured, THEN he can play first grade in his positions. Anything else is Steve Price-level idiocy.