I know this will be rhetorical to anyone who was had good results with replacing crappy transmission fluid with good stuff and suddenly having a serviceable transmission again, but having a similar but less extreme case of grindy syncros and high shifting effort in my subaru a couple of years ago that was 100% cured with Motul gear 300, I figured I'd try it in the lotus.
When I bought the car a couple of months ago, the gear shifter was a mess. The reverse lockout was adjusted over first gear, so I needed to lift the reverse ring to get it into first. The whole center console flopped wildly with every shift. If I shifted into first while moving, it ground so bad that I might as well had not used the clutch.
I fixed action and sloppiness with some adjustments and modding the shifter bracket to bolt it to the chassis in the middle. The gear shifting into first (and second too) remained awful.
Last week, I finally got around to servicing the car, and did an oil change and drain/fill on the transmission. I just so happened to have 2 and a half quarts of Motul gear 300 left over from my subaru (I overbought), so I figured I'd give it a shot.
Anyhow, at first, nothing changed. And then after driving about 75 miles and heat cycling the car twice, suddenly, first gear could be engaged while moving. No longer was a ton of pressure required, and no longer was there a Big Crunch and bang. It felt normal! And second didn't grind either! We'll see if it lasts.
The oil that came out of the trans was honey clear and smelled like Dino gear oil. The gear 300 looked much the same going in, but it performed amazingly.
We've had similar success using a GM synchromesh style oil on the Honda transmissions (I use Pennzoil). It must be related to the friction modifier (it has a lot of added Mg, P & Zn). It only works for 6 months - 1 year.