A few weeks of driving my "new to me" XK8 and I find if this were a manual box I would never want another car... ever! I have loved the XK8 style since I first seen it decades ago, and this is my first chance to own one.
The car just turned 75,000 so I figured as the new owner I should probably change the tranny fluid (it was scary under it while it was running, on jack stands).
With the known issues with these ZF trannies, I find my self grumbling at Jag for not offering the X100 line with a manual option.
The shock mounts are deteriorated and need replaced, so probably going to replace the shocks and bushings while its on the jacks.
With all of this maintenance I find it would be a loving refresh... If... I weren't a life long manual driver.
I find I am looking to cheat with an alternative car since a manual swap is just not worth it. So what are similar cars to the XK8 convertible you've looked at, 370z, Z3?

I am guessing that emissions testing/certification has something to do with it?
Every time a drivetrain component is changed that MIGHT affect emissions, the long arduous process of documenting is probably required to get some gov't approval.

Not enough demand to warrant the expense?

Xrac,
The UK TV show 'Top Gear' asked the same question as you, twice when testing the XKR and the XKR-R. Their answer was that the owners of Jaguar, Ford, did not want a market competitor to the Aston Martin DB7. Ford also owned Aston Martin so there was a potential conflict of markets. The 2 models shared DNA but the business case was always to keep market separation.. The Auto Trans kept the XK8 within a distinct GT market and this was even more apparent when the XKR was released in '98. The auto XKR out-performed the manual i6 DB7 and undercut the ticket price by ~30%. A potentially dangerous situation for the Aston Brand and the DB7 was upgraded with a V12 in '99. But by this time, Jaguar's deal had been done for a long supply of Mercedes 5sp boxes (over 7000 units), so the XKR stayed auto. There is also mention of the better marriage between a Supercharged engine and auto box. watch vids...
https://www.youtube.com/watch?v=YgzSS2fKp7k
https://www.youtube.com/watch?v=VctCdHPTqoQ

That explains so much actually. Thank you PKWise! Great fun videos to watch also.

Jaguar also wanted smooth gearchanges so they needed to link the transmission to the engine to sync the gearchanges perfectly. But I think it was more to do with Jaguars moving away from manuals for some time already so to cut down on costs it made more sense to ditch the option that not many buyers wanted anyway. Plus you have the whole Aston Martin DB7 thing. It's a shame but if you want a manual XKR badly enough you can get it done but it will cost you a lot of money.

They weren't selling many manuals, either.

As far as I know rivals such as the Mercedes SL only came in automatic form. A quick search on autotrader of Porsche 911 shows twice as many autos for sale as manuals - that could mean that more auto owners want to get rid of them, or it could mean that in the real world, outside of magazine reviewers, more people want autos than to be stuck in traffic having to use a clutch. Jaguar was just catering to its market.

Drive the J-gate, it's like a different car.

Initial buyers of these $75,000-plus new vehicles tended to be relatively settled and older. Older drivers prefer automatic transmissions by an overwhelming margin. Thus, no manual transmissions. Given Jaguar's constantly-in-peril financial condition throughout its history, that was a wise economic decision....

Yep. Missed the mark completely. I share your frustration. After watching a YouTube video, titled "How To Drive an XK8"(if I recall correctly), as mentioned, using the J-Gate makes a difference. Just be mindful, when parking, to switch back to the right side of the J. It's taken awhile to not place the car in 2nd vs Park...lol.

I, also, believe Jag missed the mark with the XJ8/R, by not offering a Coupe. Oh my!

Could have been the new XJC, would have been pretty damn sweet if you ask me. As long as it hadd no pillers between the windows like the original.

I can't seem to locate it, but a photo shop of an x350 in Coupe form is floating around on Pinterest. If only....

Hadn't seen that one. Theirs a black one also. Either way, drooling.

I should think it's possible to do a custom job but I should think it will also be very expensive to do a propper job and get it correct.

I believe they are photo shops.
Motortrend made for TV job....😅

http://artandcolourcars.blogspot.com/2014/05/2015-jaguar-xj-coupe.html?m=1