This is the reason the Mk1 is to be avoided AFAIU. The Mk1 are know for the bass drivers perishing. I stand to be corrected, but that's my understanding.
The Mk2 pair I own apparently belonged to the Kef Sales Director and have a number of the Ray Cooke features, though are not (officially) the Ray Cooke version.
Regards the cloth T33 tweeter vs the metal dome. Mmm tricky, I have some love for the attributes of the cloth tweeter, but it does lack a bit of crispness. I wouldn't say either is the perfect solution.
I agree with the bass driver issue, but I think this is now an issue with all the 107 range inc MKII (same bass drivers as the MK1) and 104/2 too, and even if it seems fine, all it may take is the extra cone excursion from a movie (The new War of The Worlds did it for mine) to tear the foam surround if slightly brittle.
I believe 10-15 years expected life for the foam and adhesives of any 107 bass driver dependent on conditions, IE central heating and such?
For me getting an old pair and having the bass drivers and treble serviced (regardless of condition) by the likes of Wembly would seem the best option, if Wembly can rebuild the bass drivers.
Any MK1 would need replacement/rebuilt bass drivers and rebuilt treble units in my opinion, any MKII would more than likely need new drivers if not a late pair, or would have drivers on their way out.
The opinion I was under regarding the treble, was that the metal dome was Kefs first foray, and not quite as refined and smooth as the soft dome, it suffered from some resonance and was a little brittle and more siblant?
Not quite as good as the units from Celestion and such at the time, and certainly not worth the upgrade premium, or using with many of the 1990 cd players of the time. My own ears prefer the cloth dome, and I feel the treble units get a little dull with age and ferrofluid drying up.
I agree with your opinion on the treble, I myself think the whole Kef 107 range's worst attribute was the treble unit, the cloth dome being the lesser of two evils. I want to change my own at some time, to a more modern equivalent, but finding a drop in replacement is not so simple, and Raal seem costly and involve work, both of which I cannot do at this time.
I am not sure there were many internal upgrades with the Raymond Cooke versions?
I also think that the 107 is less suited to the modern home.