I have to think we are a year or two away from a straight 64-team bracket, plus play-in games. I'd love to see teams seeded based on their tier and prior season finish. Then take a look at each set of four and allocate them to corners of the bracket based on geography. For example, take a hypothetical 2022 season with 30 MLS teams, 36 in USLC, and 16 in USL1:
Round 1 (44):
44 USL2/NPSL/Local
Round 2 (74):
22 R1 Winners
16 USL1
36 USLC
Round of 64 (64):
37 R2 Winners
27 MLS
For the round of 64, the four 1 seeds are the top four MLS teams from the previous year, and down the list. When you get to the 7 seeds, you have 3 worst MLS teams and the best USLC team. When you get near the lowest seeds, you have USL1 teams that won in R2, and maybe even some Local Qualifiers as 15 and 16 seeds.
Let's say the top four in MLS were NYCFC, Atlanta, DC United, and Seattle. NYCFC gets put in the East bracket, Atlanta in the South, DCU in the Midwest, and Seattle in the West. NYCFC might open away at FC Motown in a 1v16 matchup.
Would be awesome.