Most people switching to a 50trim are going to have launch control. So when leaving the line you'll already have boost. If you toss no lift to shift into the mix the lack of a BB really isn't going to make much difference.

If you dont have LC and NLTS then you should look into those first. In all honesty turbo lag is overrated. Even if you road race, most of the time you'll be above 4k rpm anyway its just not that big a deal.