My own opinion:
It depends on what you want to do with the teams. Sure, it would be
nice to spread the wealth and decrease the chance that one of your
teams gets blasted as an 0-fer for your first competition. On the
other hand, the cost is that you increase your chances that all your
teams may go 1-fer or 0-fer too. Of course, your stronger players
would all get a chance to shine and "mentor" the less-strong players
too.
Basically, I'd suggest go ahead and play around with the roster at
invitationals. I certainly think it's just as important to have a
team where everyone can work together on bonuses and don't overlap a
ton on tossups. These are all considerations which you won't really
have experience with until you start "playing around" as it were.
So in essence, for the next couple of months anyway, I wouldn't
hardwire your roster. See how things work, don't make changes too
quickly, and make sure everyone enjoys the experience, no matter how
many wins or losses you compile.