A rationalised tank
"2.) Europe currently has 3 MBTs under development (EuroLeopard, Leclerc, Challenger). WASTE. Rationalize towards a EuroMBT."
They try to do this on an occasional basis, sometimes involving the Septics too, but it never quite works out thanks to conflicting needs (or at least political machinations in the guise of conflicting needs) tending to drag a workable specification all over the place until it breaks. Even when they just try to adopt certain common standards, such as the "need" for a multi-fuel engine, look what happened: the Chieftain ended up with the export-crippling (albeit technically quite interesting) L60 at the 11th hour while the Germans stuck with their much more workable diesel and the Americans with petrol.
The current situation of technology-sharing is probably the least worst solution, even if it does leave something to be desired, and even then there's the risk it might go in the wrong direction such as suggesting that the Challenger II should use the Rheinmetall gun because of its "increased lethality"; which may be true, but it's something where the cynic in me wonders if it's just because the Americans and Germans use it - though admittedly in part because to my untrained eye it looks a bit of a one-trick pony and, well, the traditionalist in me says it should have rifling, dammit!
It isn't helped in that countries often tend to be rather parochial about this sort of thing, and in the case of the UK the random application of the rationale "it's the best because it's the most expensive" seems to factor in, too. That said, I genuinely quite like the Challenger II. Just a shame it doesn't get more international sales...
But in contradiction to everything I've just written, the British Army historically have certainly not been averse to importing some of their best weapons: looking at small arms, for example, some of the best examples were foreign designs, such as the Bren, the Vickers (even if Sir Maxim did much of the design here), the Lewis, pretty much anything made by FN... though there does seem to be a certain national pride regarding the tank. Nearly as much as subsequently moaning about our own designs! (And "guilty as charged, m'lud").