If I were them I'd keep Brock completely away from Roman and the title picture. Brock doesn't need the title anyway.
Yeah - I think Cena / Reigns is the next progression. I think now that they have Brock signed for a couple of years, they can take their time for Reigns / Lesnar. I think the reason they rushed Reigns / Lesnar was because they didn't know whether Brock was sticking around after WM 31.
The only reason I want Brock in the Rumble is for the actual match-Viking Brock, as he's booked now, would be incredibly fun in the Rumble.
A) He absolutely has to come in after New Day has gone on a run of like getting rid of 6-7 people, at which point he like overhand throws Kofi out of the ring.
B) Only way he goes out if it's a situation where all the Wyatts are ganging up on him or whoever they want to set up as his WM opponent. Hell, I'd be all for like "League of Nations vs Brock Lesnar", where Brock proceeds to turn on destructo-mode and run through all of them.
Also, Brock is so over that anyone eliminating him from the Rumble is A) instantly given some shine if they're a low-carder, ala Maven, or B) instantly given a feud if they're high card, aka Owens.
I see the following options for Lesnar
1) Lesnar v Reigns 2 (Main Event is Cena vs Taker)
2) Lesnar v Returning Star (Batista, Rock)
3) Lesnar v Bait (Owens, Sheamus, etc)
The money match is Heel Asuka VS Face Bailey.
But having Jax win tomorrow gives them more matches (Jax/Asuka) in the interim.
And of course, if Bailey gets called up everything changes.
I'm terrified of Bayley getting called up unless it is done perfectly. I honestly think her and Balor should stay in NXT and be the main stars of NXT, and be put at a level equal to the main roster. Kayfabe reasoning is simple too - Regal has asked WWE to leave Bayley in NXT to a) headline shows and b) mentor newer recruits, and that takes priority over the main roster. You can even play it up as the "dream match" that one day the NXT champion will take on the WWE champion to see who is the best.
EDIT: Tentative WM 32 card
Card 1:
Main Event: Cena vs Undertaker
WWE WHC: HHH (RR winner) vs Reigns (c)
Lesnar vs Batista (or someone else who is fine getting manhandled)
Undertaker and Kane vs the Wyatts or something
Zayn vs Owens (IC Title)
Ambrose vs Del Rio (US Title)
Card 2:
Main Event: Cena (RR Winner) vs Reigns (c), WWE WHC
HHH vs Ambrose
Lesnar vs Bait
Taker vs Bait
Card 3: Lesnar vs Reigns, WWE WHC
Cena vs Taker
HHH vs Ambrose
EDIT: A Final Four in the Rumble being Ambrose, Lesnar, Cena, and HHH would be...pretty epic, because all of them could legitimately win.