I am still in the camp of it's not ENTIRELY quantity, it's quality. The military is one extreme (lowest time, highest quality), where the part 91/61 arena is quantity over quality after a short time (more time, lowest quality). 121/135 is a median of quality/quantity.
My personal opinion is to have min time to get into the 121 world- say 750TT WITH 200multi, 50 actual, 250 XC, 100 night. There needs to be a level of learning above basic ground school- the fire hose technique works but it's a quantity of knowledge instead of quality. If the FAA wants a standard level of knowledge, run a universal class- you interview with an airline, they "hire" you and you go to a program run by the FAA BEFORE you attend the airline's ground school. The program would be for ALL 121 pilots (who already DON'T have 121 experience). The airline has to pay for each pilot. A general program (just like OKC for ATC) before being shipped to each individual ground school. From ground school have more sims with more training (yes, this also costs more money for airlines), and finally- pair up the FO with a "mentor CA" (who has say a min of 500 PIC at the company) for the first 250 hours at the company AFTER OE with a Check airman.
This idea would add 3 months to the hiring process, and some interesting contract language since a brand spanking new FO would be a "lineholder" for a months or so, but it beats the heck out of just having "consolidation of knowledge" many times flying with new (also reserve) Captains. This process also would benefit training downline in the area that Check airmen would come from flying with new guys- say 1000 hours worth (roughly a year to be eligible to be a check airman). Raise the standards across the board.
For existing crews- FO's and CA's should be in the sim together every 6 months. A rotation of a LOFT and a PC would be fine- after your initial ride you would go at 6 month intervals, for your PC you would have a day in the classroom reviewing issues on the line (and in the industry) from ASAP reports and FOQA, then a LOFT in the sim with realistic issues (V1 cut, engine lost in climbout, go arounds, Cat I/II to mins, etc.). The next 6 month would be your yearly recurrent ground and your PC (checkride items).
For upgrades- go to the upgrade ground school, sims, OE, then complete the first 50-100 hours with a mentor CA or Check airman (maybe this would be for check airmen who were mentor CA's- first assignment kinda thing).
We need to have high standards ACROSS THE BOARD. Not just hiring; it's training, recurrent, and always ongoing.
We need stronger hiring, but it needs to be both realistic and TO THE POINT. 1500 hours around the same airport instructing would not get the mins needed- which constitute some REAL WORLD flying to get to the "airline" mins. Training would improve across the board.
We also need better duty/rest requirements. Pay would come up by competition alone- the argument of "offsetting training costs" for your first year at an airline need to be gone. The first to second year pay transition needs to disappear. If second year is 35, third year 38- first year should be in the $32/hr neighborhood. ALPA and groups need to push for rigs and payrates above the poverty line. 80 hours of pay when you are working 20 days a month needs to go away- the "jet age" has been upon us for decades, we need to move away from the slow prop pay technique. Hourly works, but there needs to be safeguards of pay in relation to trips- this is accomplished by trip/duty rigs and min day. For mid and senior level trips the actual block/pay is already above the typical rigs so it wouldn't be earth shattering for the majority; but it would help overall.
Those are my thoughts on the matter.