This really depends on what you consider a 99 player. The 0 - 100 scale often used in sports games itself is a rather arbitrary concept (as is the 20 - 80 scale often used in real-life scouting), and a 99 rating only means that the player has the best skill in that rating category.
But what is best?
My impression from tweaking all these things In The Show in the past is that ratings are calibrated to recent MLB stats, which means even the 99 Contact player tends to plateau around (roughly) .320 batting average and 99 Power player tends to plateau around (roughly) 40 HRs in a full season.
If you are expecting in jacking up all ratings you can create a Barry Bonds in early 2000s, then it's not going to happen by attribute rating changes alone.
This may or may not be what you want, but The Show in the current state is rather carefully tuned to simulate the current-era MLB.