Can't speak to any 'build your own' options - but it sounds cool.
They used to have a decent pickup selector tool on their website. I almost said 'app' but this was before 'apps' really. It has been a while since I've been on their site.
What I do know is that their customer service is amazing. 10 years ago, when I first got into all of this guitar shit I bought a Duncan JB from Guitar Center for my HSS MIM Strat because I read that was the pickup to have. Well, as you probably know, the JB is not the best choice for a Strat. I called. They recommended the TB-11 (Custom Custom, which I still have today). They sent me one and all I had to do was pay the difference, which wasn't much, and send in the JB.
Easy peasy
I ended up putting a Super Distortion in the Strat and it is OK. Doable.