This makes me even more frustrated and disappointed, seeing how now that BBS is out, we know that Maleficent came in contact with the original Xehanort himself, and was plotting on achieving the objective he let her know was right in front of her for the better part of the last decade. That alone gives her a spot of honor in the series as one of the main, true antagonists.
But, alas, KHII used her as filler and an excuse to have more Heartless in a Nobody game, and Re:coded continued this farce of a treatment (as much as I love the game, Pete and Maleficent really felt redundant) with how that plot line ended.
tl;dr sure, let Maleficent stay in KHII. It's more the game that needs fixing, less her appearance in particular. And I personally prefer that fan-hype and popularity will bring back someone with the potential to recreate what she's done in KH1