A quick look suggests that the Tigris is mostly navigable up to Baghdad, which would get you halfway there.
As an alternative (and ignoring the obviously substantial geopolitical concerns), is there a geographic reason not to dig a canal on the other side of the Sinai from, say, Aqaba to Rafah? If you had to dig that far, it would seem to be the next best option.
It's kind of hard to tell, but it looks like the Suez canal was on super flat land and I recall most of Sinai is desert. The Israel-Egypt border doesn't look that flat based on the colouring on the leading image of [1].
Absolutely, I imagine the insurance alone would make the Persian Gulf route unviable. Pirates is one thing, but governments confiscating boats would be a huge disincentive. The other side of the Sinai is probably much more palatable even if Egypt and Israel aren't best buddies.
Not to mention the terrorism/sabotage/non-state actor destruction opportunities that route would present that are moderately prevented on the Red Sea side (if you can get past the Horn of Africa).
I can't see Egypt approving an alternate canal that Israel would have any control over, but I could absolutely see Israel going in on a chance to a) take business from Egypt and b) add a defensive feature along that border.
Both a) and b) would require a real increase in tensions. Israel and Egypt have a cold peace, with several common enemies/interests; the prospect of a direct military confrontation is nil, and neither side will go out of their way to harm the other economically.
The terrain along the Negev route is extremely hostile. Bypass proposals have mostly focused on rail lines from Eilat/Aqaba to the large and well-developed Israeli ports on the Mediterranean, but even constructing rail lines there is quite difficult.
An underappreciated fact of Israeli and Palestinian geography is its mountains and hills; any major transportation project [1] requires extensive tunnel and bridge work.
[1] Examples: the TLV/Jerusalem high speed rail, the Haifa highway bypass, or a proposed transportation corridor connecting the main West Bank population centers along the ridge of the Judean and Samarian mountain ranges.
As an alternative (and ignoring the obviously substantial geopolitical concerns), is there a geographic reason not to dig a canal on the other side of the Sinai from, say, Aqaba to Rafah? If you had to dig that far, it would seem to be the next best option.