Well, there's a few things I'd want for Brock's return but I think the most important thing for me with him potentially returning is the dates. I don't know the details of Brock's contract, if it's mandated that his appearances are as spread a part as they tend to be, but since Brock is no longer obligated to show up throughout the year to defend the Universal Championship, when he returns, I want him to do it one burst. Every week on Raw, every PPV, for however many dates he has left. Ideally this would be during The Road to WrestleMania, for reasons I'll get to later. I want his return to feel like he's a more integrated part of the roster, rather than some dude who just shows up when he feels like it.
Secondly, I want him to wrestle a match on Raw. It could be a five minute squash for all I care, and it likely would be let's be honest, maybe even shorter, but I feel like it should happen once. Mostly to help with the integration perception I mentioned earlier but if they care about ratings, promoting's first TV match in like what, well over a decade, is a pretty solid strategy. It shouldn't be a constant thing, once might just be enough, since you do want to maintain Lesnar's aura.
Anyway, the major thing I want for him, is multi-man matches. From what I gather around the wrestling communities online, is the general consensus has been that Brock's best matches since returning have been the multi-man matches, the fatal four way from SummerSlam (which I can confirm was pretty great) and the triple threat with Cena & Rollins (which I haven't seen but heard nothing but unanimous praise for). It makes sense of course, cause you've got other people in the match to carry the work-rate, and Brock can still deliver his signature beatdown style (and I do find it entertaining to see him just wrecking people, the problem is when he's holding the championship hostage, and almost exclusively fights in 1-on-1 match ups with similar structures to them). In particular, I want to see him in the Elimination Chamber match. Just have him enter 6th, dominate for a bit, eliminate one or two wrestlers, then the remaining superstars gang up on him with a finisher barrage and eliminated Lesnar. Lesnar remains looking strong, and he doesn't have to put in much work despite working in a high profile match, everyone wins.
Fourthly, put someone over at Mania, Clean. Preferably Lars Sullivan.