I can tell you this with both my Focuses - both MTX-75's. When I got both the shifters had a lot of resistance in them. And on one the shifter tended to pop out of 2nd gear With that particular one, the clutch wore out and when I replaced the clutch, I made sure to get every bit of fluid out of the transmission, (since it was out of the car it was easy to tilt it) and I replaced it with the $20-a-bottle Ford synthetic manual transmisison fluid. The change in the shifter feel was like night and day and it stopped popping out of 2nd. I had half a bottle of the stuff left and I put it in the other Focus since I noticed it was a bit low - and shifting also improved although not as much.
I would possibly consider TRYING Amsoil Manual Transmission & Transaxle Gear Lube 75W-90, or the Royal Purple MaxGear 75x/90. But you really have to be careful with the fluids in the MTX-75. ATF is too thin and won't lubricate well, this trans must use a gear oil. But, regular dino gear oils are often high-sulfur and those will ruin the MTX-75 as they will corrode the transmission.
The Amsoil states "protects brass synchros" and the RP gear oil says "it is non-corrosive to soft metals, brass, copper, etc.) in their sales literature. THAT is what your looking for in any MTX-75 fluid. Fluids like Redline MTL and other hypoid gear lubes have high sulfur content and will oxidize the transmission. This has been argued over almost a decade ago since Ford used this same transmission in the Contours and a lot of people raced them. The fact is that Ford has a lot of trouble with the MTX-75 in the beginning because they didn't recommend a special fluid. Ford ended up having their synthetic manual transmission fluid engineered specially to solve these problems.
Frankly I don't understand this interest in the non-Ford fluid. The Ford synthetic fluid can easily last 100K miles in an MTX-75 and at max you use 3 bottles of it. The Amsoil and Royal Purple and other suitable fluids cost almost as much as the Ford fluid you may save $5-$10 a bottle. So for a trans flush that will last easily half the life of the transmission your going to save $15 by using aftermarket fluids that aren't engineered for this trans? WTF is that all about? Is getting the Redline sticker out of the box so you can stick it on your bumper really that important?
You should try dealing with a Chrysler 41TE one of these days if you think paying the premium to Ford for their ATF is that bad.