Most would consider this cartridge a barrel burner, but it's really just an indulgent experiment for an old but accurate 223 target rifle. I think it is worth comparing the two.
The Middlested can be formed from virgin brass and has a long neck that's good for seating VLD projectiles. It apparently helps reduce throat erosion as well.
The Ackley has greater powder capacity (the purpose of this cartridge) and the sharp shoulder angle apparently reduces throat erosion, although it has quite a short neck.
Opinions?

I had the same bug only I made it even more complicated. I just had to have a QT .224 on a short fat case so I designed one and it requires mulitple form dies, cut off and reaming.

The net from this rifle compared to a Swift is that the Swift kicks a little less and shoots the lighter bullets just as fast. By the time I got loads developed the barrel was soft.

If you must do this then pick a case that's easy to just use as is and go with a QT like 1-8. I suggest the Swift case. For more capacity the 6mm Rem might work. There is the .223 WSSM you know!

I don't think the neck length matters, nor much of any of it insofar as erosion is concerned. There are some that think the 35* shoulder superior to the 40*, and I won't argue the difference.

Not just my opinion but a philosophy I concur with:

A cartridge case is nothing more than a gasket that contains(hopefully) the pressure and directs it out the muzzle. Any effect its shape has is fairly minor. Yes, probably, maybe, there are small gains with one versus the other, but they are very small, and apparent only to those that analyze the last small percentage points, or fractions thereof, and have the equipment to really do that. Expansion ratios hold sway over the bulk of internal ballistics, not case shape.

Throat erosion is a product of pressure and it's really not erosion, but that is another subject. Given modern propellants and barrel steels, it is predictable like rain, or sunrise. If you don't want it, stay out of the high end of the pressure curve. Or, have a stellite chamber insert installed when the barrel is built.

Oh, and I always lusted for one of the .22 QT's perhaps like the one based on the Bob case, 1:5.5 and a 125 gr bullet. I have no idea on earth why.