The biggest problem with a giga church is that you have to be really really good to make it into the worship group. Our back up guitar player is a five time grammy nominee.
Yes, it is a problem, but you can start your own group using church members and sing in other places. We do a lot of singing in retirement homes and hospitals.
Nothing says you are limited to worship in the sanctuary. Quite frankly, outreach to people who really need His love is as important as "singing to the choir" in a worship service.
Possibly more important.
Also, you have creative control.....hehehehe