What really disadvantages the mid-major powers is not that they can't get enough top-50 or top-100 games (although that is a legitimate frustration). It is that the RPI punishes teams way too hard when they play sub-200 or sub-300 teams.
This is, at best, an oversimplification.
Let's look at the case of Rice. C-USA is a weak conference: 8 of its 14 teams are outside the RPI top 150, including 3 sub-300 teams. Despite this, Rice's RPI has risen from about #100 at the start of C-USA play to #34 now.
Let's look at Quinnipiac, a decent team in an *extremely* weak conference, ranked 26th out of 32 D-I conferences in the RPI. Eight of the MAAC's 11 teams are outside the RPI top 200. But Quinnipiac's RPI, like Rice's, has *improved* since the start of conference play, from the mid-60s to #44 right now.
There is certainly a difference between playing the #120 team and playing #320. Just from a statistical standpoint, top-50 teams lose to teams in the 101-200 range far more often than they lose to sub-300 teams. The following projected at-large or bubble teams have losses in the RPI 101-200 range: Marquette, Syracuse, Rutgers, DePaul, Central Michigan, Kansas State, UCLA, Buffalo, South Dakota, North Carolina, Michigan State, Indiana, Clemson, TCU, Tennessee, West Virginia. But of the teams currently projected as at-large or bubble teams, only BYU has a loss to the bottom 100 of the RPI. (Miami of Ohio, a fringe bubble team, also has a loss in this range.)