There was a time you didn't have to be so consistent to be #1.
Del Potro could easily make it, he almost made it in 2010 before his injury. That run he was on would've been enough in another era.
You needed some degree of consistency though, which the names in the poll bar JMDP were never capable of.
Yes, Del Potro won 1 Slam, made 1 SF and 1 QF, F at WTF, QF-F in 6 of the 8 Masters he entered... I'm sure there have been former #1s with worse numbers over 12 months ie even with the injury happening he could have had a shot at it in a non-Fedal field, not to mention that in such a field his result would have been better since he was stopped by Fedal at 2 Slams and 3 Masters. Apart from pre-surgery Del Potro though, I don't think any of the other names in the poll would have even a puncher's chance at #1 in any era though.