Drafting that many players would likely result in too much stockpiling. It would favor the owners who never want to trade, but only draft and stockpile. For leagues that have vacant teams, it would make the problem of talent that is locked up and can't be traded for worse.

There needs to be a balance between owners who want to stockpile and build through drafts and those who like to trade, but this tips the scales way too hard towards the more conservative style. Why would you even look at your team after the drafts if this many players were locked up and half the owners were non-traders?

Dave N