I don't see the problem here Or I am not clear with what you are saying.

I meant by avoiding REORG, avoiding FRGMENTATION, utilising space in efficient way, doesn't mean by not touching (monitoring) it at all. Thats what I do, I estimated future growth and give enought space and monitor it and when my tablespace is say 90% full, I add one more datafile of 2GB.
I will make sure that segment level storage clause will be taken off.

Monitoring space requirements is part of DBA life no matter you use locally managed/dictionary managed cuz, at somepoint of time disk might ran out, thought you use locally managed tablespaces. so, you have to anyway.