Would it not be better to develop Watson as our FB and leave Henderson as our CHB! IMO, we have significant options already for our CHF / FF combo without adding Henderson to that mix (even though he would fit in there easily, imo I would prefer a settled back line, which he offers).
Something like this:
B: Jamison, Watson, Laidler
HB: Duigan, Henderson, Yarran
I don't know and I still have reservations on a couple of those guys finding their best positions as you have outlined.
The starting back 6 will be pretty much be the statement of which way MM wants to go.
Of course there may well be enforced changes but he'll give that opening 6 the best opportunity to gel together. A luxury we haven't had in the past few years.