As far as Tyjon goes I think it's instructive to think of the 9 and 10 role together. Across the two roles we now have four players - Ohashi, Gueye, Tyjon and Cantwell. I think without blocking Tyjon we need at an absolute minimum one more in there. Ideally someone who could play either as a 9 or a 10 as I don't think we can have only four players for two crucial roles, especially when we get into the November to February madness.
Even if we count Tyjon as a new first team squad player (and we should) five players in those forward position who have left (Dolan, Weimann, Woodrow, Dennis, ACB) so we are four short. Getting one more back in is the absolute minimum imo.
In May last year we had eight players (Ohashi, Gueye, Weiman, Dolan, Dennis, Woodrow, Cantwell, ACB) who played across 9 and 10. I am sure we will sign someone. Maybe two. And that would be no real impediment to Tyjon, he will get plenty of game time.