First, I have no idea whether Miles is pursuing the best graduate transfer in the market at a position of need for Nebraska. But I imagine that since Mekowulu's announcement on Saturday, he's at least asked around.
Second, Christian has improved his FT% from 59 percent to 64 to 75 percent in his three years at TSU. That allows you to potentially tell Christian and Jordy: "There's 40 minutes out there at the 5 spot for you. Let's see who gets 25 and who gets 15, or if you'll split those minutes more evenly." There's no need to sub out at the end of the game unless you simply want a shorter lineup.
As already noted, Mekowulu (or a player like him) allows Roby (4), Copeland (3) and Palmer (2) to move down a slot in the starting lineup and then to mix and match the 3 and 4 spots among those three players after you start substituting. We aren't especially deep in the front court right now, and with Isaiah not having to match up with bigs on a regular basis, he might not foul as much and be available to play up to 30 minutes per game in tight games.
It also allow you to have more length and athleticism in the backcourt when it's needed. If Thomas Allen emerges as a legitimate Big Ten player this year, then you can sub him in at both the 1 and 2, even if Amir Harris doesn't emerge as a legitimate point, even if Nana or Thor don't emerge as rotation players.
Bottom line — we really have only six rotation players we can be confident in at this point, and that's not a recipe for success in the Big Ten. A player like Mekowulu puts us at 7, and really requires only one of Harris, Davis, Nana and Thor to develop into a top-flight player for this year to get us to an 8-player rotation. We're not looking to just be better than Nebraska has been. We're looking to be a legit top 25 team and a contender for a Big Ten title this year. A player like Mekolulu gives us real chance to do that.