Hey bud,
First and foremost, let me tell you that I know first hand what it feels like to have a coach try and fix something that ain't broke. In college, I threw a sinking low-90s FB and an above-average CB but my coaches were constantly trying to change my arm action and get me to throw a SL that I could just never seem to get a "feel" for. I know they had the best intentions -- and some of their advice may have even been beneficial! -- but they just didn't go about it in the best way.
Here's what I think:
If your goal is to play beyond a low-level college program (if that) you absolutely need to resist your coach's desire to turn you into a "crafty lefty".
You're set to graduate in 2017. Which means you're at a premium stage in your life to make massive changes in your athletic ability.
There is absolutely no reason why you can't develop elite-level velocity in the next 1-2 years with the right kind of training. (I'm talking the kind of velocity that gives you the chance to play in college and/or beyond.) And, seeing as you're familiar with Austin Wasserman's and Driveline Baseball, you seem to be on the right track in that regard.
My advice would be to approach your coach in private and let him know that you have a desire to play baseball for a good college program and that you understand that improving your velocity is going to be a big part in making that happen. I would then mention that you've been feeling/seeing great improvements with your current program and that, although you're open to suggestions, you don't want to try to fix something that is not only NOT broken but actually seems to be working quite well for you at the moment.
And if you're worried you might upset your coach and you might lose playing time as a result, I would take the gamble on reduced playing time in the short-term for the sake of your long-term development.
Hope this helps and best of luck. And please let us know how things turn out.
Tavis