This gem thing sounds kinda pretty awful, on several levels, with only a hint of "well...maaaaaybe this could work." As for why it's awful, eh, it's pretty much been covered by everyone else at this point.
As for Capcom and their awful PR lately - to break the cycle they have to do something, something BIG to show good will to the fans. Telling the fans "hey, buy this 40$ DLC and make your old 60$ disc obsolete and useless while you're at it" and "Hey, we're canning MML3 and throwing away the who knows how many hours of player done work that our fans did for that game" and "here's this gem system, by the way, pre-order bonuses and dlc and collector's edition exclusive gems, so, you know, keep paying us if you want to stay competitive in this game" and "here's the new DMC game, out of nowhere, done by a totally different team with a totally new Dante!" and "We heard you liked iterations of Street Fighter, so pay us 40$ to obsolete your 60$ game, and then we're going to balance the game a short time later by adding clearly unbalanced characters to the game!" (not to mention things like the RE4 and RECVX collection games and their minimal effort do anything with either of those games) and just one thing after another after another and making all of these questionable, if not down right money grabbing moves and telling the fans "but it's ok, because next time we'll treat you better!" and then doing it again... and then again... There's just no reason to believe Capcom is willing to do anything as a sign of good will towards the fans, even minor things like making an "ultimate" or "super" iteration of a game cheaper DLC, or release their fighting game that will assuredly get an iteration 6 months down the line cheaper than 60$ at launch, and so on. They burnt their good will towards the community at just about every turn they could, and they have no one to blame for people being upset at questionable moves but themselves at this point.