Slew O Gold won the last triple in New York, which I believe was the Marlboro Cup, The Woodward, and The Jockey Club Gold Cup. I was there that day (it was a rainy day), and I think the 10,000 or so there were the only people that cared. I also remember Mom's Command winning a filly triple, the Acorn, Mother Goose, and Coaching Club of America Stakes.
I think what differentiates the current Triple Crown is you have 1 shot. Having said that, I think if the Triple Crown was to be spaced out a little more, you could have THE Triple Crown (Derby Preakness and Belmont); on Friday have the Filly Triple Crown (Derby, Black Eyed Susan, Coaching Club); A Turf Triple (Woodford, Dixie, Manhattan). Uh oh, I went Triple crazy didn't I!

Here is the list of G1s for the Handicap division excluding races on turf and mile races (Cigar Mile and BC Dirt Mile excluded, keeping Met Mile).

DONN
SANTA ANITA H.
MET MILE
STEPHEN FOSTER
WHITNEY
PACIFIC CLASSIC
WOODWARD
JC GOLD CUP
AWESOME AGAIN
BC CLASSIC
CLARK

No offense, but right off the bat, you'd toss the Donn, the Stephen Foster, and the Clark. The Big Cap is hard to toss, but since the BC is so frequently at SA, and with that being the finisher, you'd probably throw that out as well.

Maybe an 8f, 9f, 10f progression, finishing with the BC Classic.

My vote would be Met Mile, Whitney/Woodward, BC Classic. So you've got a June/August/November calendar.

1st, to the history buffs, what horse(s) has already done this?

2nd, this obviously wouldn't capture national spotlight but would be fun for race fans.

3rd, this looks like Palace Malice's current plan. So let's root him on for the Senior Triple Crown (sorry, crappy name).

EDIT: Just realized that having first two legs as NYRA probably wouldn't fly politically. :) Still needs tweaking!

When Meydan goes back to dirt, all the top older US dirt horses will try to get there...and be on the shelf for months afterwards, coming back to prep for the BC.