I'm on the "trade-up-for-Darnold/Rosen/Mayfield-and-heck-no-to-Allen" wagon, but if I had to make a case, then I would do it for Jackson at 12.
My argument would start with this:
When asked which teams he met with, the Buffalo Bills were the first team he mentioned. Jackson ran the Erhardt-Perkins offense at Louisville. That happens to be the same offense Bills offensive coordinator Brian Daboll is scholed in. Jackson is more than confident he can command that offense in the NFL, too. http://www.newyorkupstate.com/buffalo-bills/index.ssf/2018/03/lamar_jackson_steals_show_at_nfl_combine_meets_with_buffalo_bills.html