Why not have the following procedure to select papers?
Day 1: submission deadline
Day 1 to day 3: assignment of submitted papers to PC members
Day 4 to day 9: physical PC meeting at some location such as Dagstuhl or NSF to read, discuss, and select the papers
Day 10: list of accepted papers is made public.
The work for PC members would be concentrated in a single week, more efficient.
Authors would get results almost immediately.
There would be much more interaction between PC members, which would be a much more efficient way to read, learn and form an opinion about submissions.
There would be a clearer distinction between conference and journal evaluation.
The total amount of work per PC member would be reduced.
There wouldn't be time to get outside expertise except for emergencies.
The type-A PC members might dominate the decisions.
PC members would be spending that time away from their families.
Would any conference center be willing to let a committee use their space for that?