@Bones:
I need to check something with someone (matchup ratio on each stage is actually very important to this discussion) before I fully flesh out my response through example, but in the meantime:
Reducing the difficulty of the stages played on is not one of the objectives of the DSR change.
The objectives thus far were to increase the number of stages played on during sets to test player ability on communally determined "fairest" stages, and to adjust the advantage gained by taking a first round win and keeping a match lead throughout a set.
With the current system, we will see players play on stages that their characters have the greatest disadvantage on in the second and third match. This has a twofold effect. The first is that the straight odds of the matchup will more frequently lead to a round 4/5 as the set lead is gained and lost. The second is that the players will be tested frequently on stages that their character is weak on in that specific matchup, and we will see a development of character strategy on stages/matchups they are generally regarded as being weak in.
To state again: These are not things we are trying to avoid, given that those stages have been determined as a level playing field for all matchups (not necessarily even, but not an easy win for either character either).
With your system, you are actually increasing the reward for winning the first match, and increasing the reward for maintaining the set lead. Being allowed to go back to a stage you have previously won on gives an inherent psychological advantage due to the mentality provided to that player, as well as the inverse to the other player, despite it being played on a stage that would be considered "even". This has already been covered in previous posts.
The biggest issue I have with your system is that it is reducing the number of stages a player MUST be proficient on in any given matchup from 3 to 2. With that method, a puff player would only need to practice on FD and FoD against Falco, and never care about any of the other stages, as long as they win the first match.
In a best of 3, this would be seen as "FD, Loss, FoD".
In a best of 5, this becomes "FD, Loss, FoD, Loss, FD".
In a best of 7, it becomes "FD, Loss, FoD, Loss, FD, Loss, FoD."
This is a very personal and biased statement, but I absolutely ****ing hate seeing tournament sets played out like that. And it only gets worse because the opponent can't ban FD or FoD or they will get taken to the worst possible stage for their character in the matchup, so they end up stuck in the loop.
This is all theorycrafting though.
Also, for your numbering method, it would benefit from using matchup win percentage based on stage rather than what you used. Ideal in a 5 game set would be 2.5 for completely equal matches on all 5 games. (Which isn't actually what we want.)
The switch to DSR only works because we have removed the "jank" CPs. The jankiest a CP can get is PS (currently, still haven't decided about its status). Even if the Falco player is at a slightly larger disadvantage game 5 according to matchup %, it is not beyond the threshold that would make it unfair, as that game 5 will not be on par with having to play a stage like Brinstar game 5.