Speed+Strength= Power so yes being stronger and faster will definitely help with Baseball. Wish I was still playing but quit to pursue more education after a Knee injury freshman year.
Winny will be hard on the joints. You can take it with a low dose of Deca. A few guys on my team did this.
Work hard on a speed and power program before the season. Sprints, uphill running and Stadiums.
Also do Plyometrics and other power building exercises. Then in season cut it down and try and maintain. Look at Sammy Sosa that guy is huge and bloated in the Spring and looks very much leaner around midseason.
I think Barry B. hit it up the last few years. He already had a tremendously quick bat and ecent power. Add a shit load of strength to that combination and bam 70+ Homers. Big Mac was 210 early on. With the same talent and 40 more lbs of muscle his home runs went up an up.
It won't make you better talent wise. If you can hit, you won't hit on roids. But if you are in the middle, very quick and fast bat, or arm motion, add strength in those movements and bam a lot better performance. Faster velocity and farther and longer hits.
It has to do wih training. Don't go into a hypertrophy phase and hope to get more performance. Keep in lean, and get into some good power routines. Deads, Suats, Squat Jumps, Pichting for you, and sprints, sprints, sprints and then some long distance work every once in a while for the endurance in those long season's.
Oh yah more velocity doesn't only come from arm speed. It comes from the Hips, ass and Legs. Look at Roger Clemens, Kurt Schiling, now guys with long whipping motions can also move it, but they also get a lot of Arm injuries because of that. Oh yah and Nolan Ryan. Check out the Wheels on these guys and you'll see where the power and stamina comes from.