Which 2-seat 4th generation fighter/engine/configuration (de-militarized) would the best supersonic long-range civilian private transport? Seeing recently -with some surprise- that former military jets of fairly recent vintage can be bought e.g. here and operated by (skilled+licensed²+rich³) private individuals after all classified/restricted tech has been removed, I was wondering what plane would be best suited for a Max-Fuel configuration.

I think I use the right terminology and assumptions, but for clarification:


2-pilot-seat configuration: "Learner configuration", like in driving school, where both seats can "pilot".
I'm assuming, for every modern 2-seat airplane a "learner" version/configuration_kit exists.
Super-Cruise: I believe is a supersonic mode of travel without using the Afterburner
Gen-4: I believe this includes F16 and newer (and foreign equivalents)
Gen-3 and older: There aren't any Super-Cruise-capable specimens?
I believe, all civilian runways are long enough for Gen-4 planes
I'm assuming, using afterburner absolutely kills max range.


For example, Wikipedia says (ballpark numbers) an F-18 weighs 15 tons empty, and has a max take-off weight of 30 tons. Internal fuel capacity + maximum external fuel capacity is 12 tons. I'm assuming the remaining 3 tons are the ammo for the Vulcan Gun, flares, the pilot and other stuff you can drop or shoot in order to have a minimum onboard defense/offense power, and not just fuel. Wikipedia seems to say in the specs, that it can travel ~2300km with ~6tons of fuel.

I'm assuming, that a de-militarized version of this 15ton bird will be quite a lot lighter, i mean, no [gun, ammo, flares, armor, ECM, cameras, etc.] needed. I'm guesstimating that could slim the plane down to say 12 tons. I'm aware, that not all the remaining ~6 tons could be used as additional fuel weight, but by converting the gun/weapons bay to big tanks, and running fuel lines to the missile-mounts, surely a large chunk of that could be converted to fuel weight. 

So, the above looks like an F18 learner could be "converted" to a max-range-model 2-seater "sports-car-for-the-weekend-trip" with a fuel capacity of ~16 tons and therefore a range of ~5700km. That gets you over every ocean.

Now all of the above does not take into account the fuel usage at Super-Cruise (iiuc), and I have no idea which plane/engine is the most "efficient" in this speed envelope.

SO, basically, my question is:
Which plane would a "bezos-rich" person buy, if he wanted something for super-sonic weekend trips with his (also former air-force-pilot) friend, and what modifications could/would be possible to extend (super-sonic) range to achieve the best average speed. Is it fast enough, or even possible (w.r.t. time-zones)  to have brunch on both sides of an ocean?

@ManuH pointed to a great example from pre-jet-times, the business exec version of the Cavalier_Mustang

@RonBeyer: Don Kirlin bought 40+ air-worthy F18s from the Australian Airforce

Edited to address comments.
"Best" is subjective. At the very least, you need to prioritize your criteria for the question to be fully answerable.

I'll give a short answer based on your current criteria:


Civilians can potentially buy any fighter jet, provided it's demilitarized, depending on their relationship with the government. The US certainly won't sell an F-22 or F-35 to just any individual or country, but George W. Bush might have a shot. Absolute monarchs, of which there are quite a few left, might buy a jet for their military and appropriate it to themselves.
No recent fighter jet is even remotely close to being flyable by someone with only a PPL, even with every endorsement out there. The ground is severely obstructed in these planes while landing, their stall speed is uncomfortably high, their control sensitivity out of the ballpark. The only civilian-piloted case for them would be a retired fighter pilot.
No fighter jet is capable of long-range supersonic flight. The supersonic range of all fighters is extremely short - a few hundred miles for the best-case. The only military aircraft capable of sustained supersonic flight are the B-1 and the Tu-160.
Not much weight can be removed from a fighter jet before it's easier to buy two fighter engines and build an experimental aircraft around them instead. The gun and the main radar is about it.
If one had to choose specifically a fighter jet, the best choice is perhaps the Su-34, thanks to its amenities, as well as its long range and large useful load.
Of course, with unlimited choice, the Concorde would still be the best. Out of military aircraft, the Tu-160 - it's got enough in common with a supersonic airliner to convert, and it's the largest.  
If SST and bombers are out of the picture, you'll get where you're going fastest in a fast bizjet like the Global 8000. The F-18 is not suited for the job at all, as it's not even able to supercruise. A fighter jet can be fun to fly (if you can do that) for the performance, not for its usefulness as a transport.