Without reading the entire thread, the initial premise that one can't turn more than 90 degrees off the runway is ridiculous and foolish. There is no such rule, and it's done all the time. The only difference in the amount of time it takes to leave the runway. A high speed exit is designed to expedite leaving the runway, whereas other exits are not. Going to the "reverse" high speed is not a violation of policy or regulation that I'm aware of anywhere on the planet.
I've done it at many airports in the United States and around the world.
For us, reversing on the runway is a big deal. We require 153' to turn around and reverse on the runway, or in other words, to go the other way. If our body gear steering isn't armed or operable, we need 170 feet to do it, plus 50' in front of the nose for obstacles at the time, and 12' past the wingtips due to the large antennas that trail on the wingtips. The 153'/170' is just the hard surface. This also comes into play when considering how much we will need in a turn; a reverse type exit requires more distance, and unless it's a combination of exits that has more pavement, usually the reverse doesn't have a wide enough entrance to allow us to do the full turn.
Where the reverse is wide enough, we can do the turn. We're going to need to be below 10 knots to make the turn, and generally much slower if we're making a large turn; we'll also be carrying power in the turn, and if there are loose objects of sand or dust near the runway, we're going to be obscuring visibility near the runway and on the airport, for a short while.
Beyond those considerations, there are no rules which dictate we can't take the high speed ahead or behind. My personal preference is to roll as far down the runway as I can in nearly all cases, to save the brakes. Hot brakes are always an issue for us, and I roll long in light for heavy airplanes. It doesn't matter.
Commonly a tower will dictate the taxiway to use when exiting the runway. Unless they tell me to exit at the end, my response is generally "unable." I don't accept land and hold short, and when I'm landing, it's my runway. If I'm able to get off the runway early and tower tells me to continue to the end, or to continue past an exit, that's fine. A couple of years ago we were working frequently next to a couple of high speeds that couldn't be used because of de-mining operations; we had to continue past them, and that's not a problem. What is a problem is ATC dictating taking an earlier exit than one wants or intends to take.
Insofar as a high speed going the other way, or not, there's no prohibition against taking one. It is NOT reversing direction on the runway, and I very seriously doubt that one will be able to produce a single case of a pilot being in trouble for taking such an exit. If indeed an individual has come under scrutiny for that action, it's the extenuating circumstances, and not the use of the "reverse high speed" that did it.