I would keep a 12-PPV schedule. I'm also on board with the consensus that the gimmick PPV's have extremely devalued the specialty match types like Elimination Chamber, Hell In A Cell, and even to a lesser extent Money In The Bank. For this scenario, I'm considering that WWE reunifies the world titles, but keeps two separate midcard titles.
For simplicity's sake, I'll say each is the last Sunday in the month listed.
January - Royal Rumble. One of the Big 4 and a tried and true classic (and subjectively, my favorite PPV of the year). Main event obviously being the 30 Man Rumble with the winner getting a title shot at Mania.
February - No Way Out. Main event of either Hell In A Cell/Elimination Chamber, depending on storyline requirements, to bring those match types back from oversaturation.
March - WrestleMania. Money In The Bank Match under the original format. Opening match, is valid from later in the night to main eventing the following year. MITB was so much more interesting and entertaining when tied into the Mania stage instead of July.
April - Payback/Backlash. Dealer's choice. Blow off feuds that didn't at Mania. Take care of any "rematch clause" matches.
May - One of two rotating PPV titles. You can utilize some other older PPV titles for these, No Mercy, Armageddon, Unforgiven, Judgment Day, or even a WCW title like Spring Stampede for this particular one. A One Night Only type event could also work into this set, do a WWE Old School (with a blue-bar cage match main event or something similar), One Night Stand, Cyber Sunday/Taboo Tuesday. The possibilities are endless for these and can keep the schedule fresh from year-to-year.
June - King Of The Ring. Single night 8-man tournament plus WWE/Tag Team title matches. IC/US champs in the tournament by default, plus 6 other upper midcard/main event tier wrestlers. No title shot or prize (or stupid Royalty gimmick change), but should be used to launch an upper midcarder into the main event scene.
July - Bash At The Beach. Should be an outdoor event if at all possible.
August - Summerslam. No tweaking needed. Big 4 event to cap off the summer boom before football/other TV starts up.
September - 2nd rotator. See March.
October - Halloween Havoc/Fall Brawl. Always my favorite time of year for WCW PPV's, and the concepts they ran were also superior to WWE fall-season PPVs.
November - Survivor Series. Featuring traditional SS 8- or 10-man tags, with a few title matches. Combine elements of Bragging Rights/War Games/Battlebowl to restore this PPV to it's former glory as the highlight of the year for team-based match fans.
December - New Year's Revolution. Great launching point for storylines where a wrestler is shown refocusing themselves for a better following year, beginning their push here. Starts the Rumble speculation and begin to form the card for Mania.