Suppose you are 1K once the merger is done. Then you will likely be able to book yourself into an ELR seat every time.... Having extra seats in F could make a big difference in terms of upgrade percentages.

The biggest drawback of not having E+ for top-elites are in situation where reservations are made/changed close to departure time.

I am surprised that many seem to suggest that additional upgrades cannot make up for an occasional seat in E-.
Is E+ really that good... (my signature reveals by lack of experience in this regard)... or is it E- which is that horrible?