My first thought would be to use the loadout system some - you can build multiple loadouts for a single character, say a "hitter" one in which after you "max out" your hitting you put some fielding / speed perks on and a "pitcher" one in which you carry zero hitting perks but instead a full slate of perks that helps your pitching.
And on that subject, a lot of which perks are the "most useful" depend on the type of pitcher you're building. "Watering him down" by boosting all the stats a little isn't as "effective" as putting a serious boost (read: 2 or even 3 perks) into what matters to your pitcher the most (or second most). Some examples:
One of my "favorite" builds is a Control pitcher, with a 4 seamer, changeup, curve, slider, sinker. I'll "double up" on Control perks (I use pulse pitching - so a "standard" control perk with the secondaries I want along with Conductor makes my pitches pretty accurate - in 22 on a knuckleballer, I had the pulse down to a quarter of the strike zone with the "horrendously inaccurate" knuckleball. Then I usually double-down on break, since 4 of my pitches are "break reliant", having the double-break leads to a few more "swing & misses" because they aimed at the "start" of the pitch, not the end. If I did a single break and velo perk, I might get 1 MPH on my FB, but lose "an inch" on the break of my pitches, so more foul balls and/or put in play outs vs. strikeouts
ps: the loadout system allows you to put custom gear on as well, so for my SP/XXs, he'll use a more fielder-statted glove and cleats while batting, and a glove / cleat combo with stamina / K9 while pitching...
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