The system is dropping the +5 flat bonus and instead having stat growths from level ups again. Players pick the bonus they want from the five options as before. If it proves to be messy then I'll put it back to the static stats. The rank options themselves will be reviewed.
That sounds good. As for changing the Rank Up Options, I personally really like Red's choices for Rank Ups. His choices make it very clear and easy to build him as desired without the worry of "wasting" rank ups or feeling like you're not using him right. I think reworking everyone else's Rank Up choices to be similar to Red's would work great.
Another option, if possible, would be to give players the freedom to simply choose how many sources (out of a fixed number per rank up) of whichever stats they want on a Rank Up.
For example:
-Give the players, say, 20 "Points" to "buy" the sources they want for the rank up
-The player "buys" 10 Power Sources, 6 Speed Sources, 2 Guard Sources, and 2 Mind Sources for Tifa
This would especially help later in the game if players find that they didn't invest enough into a party member's defenses early on, while not having to "waste" a Rank Up or two to patch up the low bulk and get stats they don't want to invest in (such as Strength on a Mage character).