Just recently we asked ourselves the same question... Why not take the advantage of the altitude gain due to the commanded FD-pitch of 20°, 22° or even 25° before the potential WS kicks in? Anyhow: we didn't recall a specific pitch limit on TO.
And how about you flap limiting speeds if keeping the pitch at or below 15°?
And how about reaching 2nd segment requirements?
And so on...
Hmm, this guys is outaline...
N1