Ok let me flesh this out a bit and give you why I really doubt sentinels' flexibility.
Let us look at nrg who has hard role players.
Ardis - sage/jett
Crashies - sentinel/initiator - known for init.
Fns - sentinel/init - known for sentinel
Victor - sen/init/2nd duelist known for mainly 2nd duelist
s0m - controller
Notice how all the flex players enable the hard role players to keep playing their role and if they take away one, they can alternate amongst themselves. Especially notice if ardis wants sentinel, victor is suddenly enabled...4 of their players are pretty much ALWAYS in ideal roles (notice how init is specifically flexed between role players where 2 inits is very common)
Sen:
Dephh - best role is sen as you said. 2nd best char is controller
Pancada - hard controller
Zekken - best chars are sova and 2nd duelist
Sacy - hard init
Tenz - hard duelist with sage i guess even though he's never shown that before...
Dephh is fucked if tenz needs to ever not go jett UNLESS a 2nd controller is somewhat viable?? And you want zekken to play hard init when he was the 2nd or 1st man in on xset as the costar?? (2nd time ever on breach btw, which is a lot more of a selfless character). The role players DO NOT SHARE a role pool and instead share with role anchor players. And that anchor players in my eyes.
This is why i doubt sen so much. The pieces are good but I don't think this team gels well unless they can vastly improve in their new roles