Despise conventional dome tweeters

I despise conventional dome tweeters! Is it just me who cant stand their nasal sound with added coloration of the baffle and rear pole piece reflecting the back waves, back forward...?
That is certainly a broadstroke critique if I have ever heard one. I agree that there are bad metal and cloth dome tweeters out there, but fewer than there used to be. There are also many good, and a few great ones, although I certainly notice the difference between domes and ribbon tweeters. Anyway, if you hate them so much, why did you buy the B&W and the Quad speakers?
I tend to listen first to systems. Then, when I hear something I like, I dig in to understand the technology behind it and why it delivers the sound it does.

I think its counterproductive to get too obsessed with a particular tweeter design alone. You have to look at the whole system and how everything sounds together, be patient and listen for a while to really hear what's going on.

Tell us what tweeters/systems have you heard that you like and I suspect you will get a slew of recommendations of things to try.
Try listening to some Gallos, I find their tweeters to be superb...

GO HORNS! Efficient too!
Well okay, I guess I was a bit brash...

This is where I come from. My high-end journey started out with QUAD 57 ESL speakers (no-brainer!) but I had to let them go as they too up too much space.

Roxy, I should have included the next few lines: Please note that I use the word "conventional". My B&W P6 speakers had the most lovely tweeters; io, they disappeared in the sound-scape. They were most certainly not conventional. Metal alloy dome, very powerful magnet, small baffle space and good weight behind them (well coupled).

The QUAD 21L speakers have "conventional" tweeters and they draw too much attention to themselves.

Spendor S9e speakers have bloody fine tweeters.

B&W 704 have sexy tweeters.

Sonus Faber Cremonas have elegant tweeters.

Yeah... I am p!ssed. Pardon that. I just cant stand a bad tweeter. My quest continues for better speakers.
Crossovers and overall integration of the design is the key, not whether its a dome or not.. They can work in the right application just as well as any other driver that somebody puts the magic behind to optimize its capability.
A lot has to do with driver integration. Tweeters are really very simple and very easy and cheap to make and they perform better than every other driver.

If you notice the tweeter at all then it is a bad speaker design (very common).

A good design (rare) will not sound like two or three drivers coupled together - it will just sound like music.

I had B&W P6s for years. You're right, the tweets did disappear nicely. I suspect though this had more to do with the voicing (overall tonal balance) of that particular speaker and how it played in your specific system more so than the tweeter itself.

You're probably getting a somewhat brighter tonal balance with your current Quads in the same system compared to the P6s I suspect.

Short of changing speakers (those Quads are fine speakers IMHO) you might be able to get the sound you're looking for out of the Quad 21Ls with different interconnects perhaps first.

You might try DNM Reson interconnects, which are not too expensive. These ICs are very British, refined and mellow sounding on the top end. When I use them in my system the sound reminds me greatly of the highly unobjectionable top end of the P6s when I owned those.
You might like to try the Mirage OMD-28. I really like the Mirage tweeter. It's a pure titanium dome with a cloth surround. The titanium makes the dome very light, rigid, and fast while the cloth surround damps out any ringing.

The OMD-28 and OMD-15 floorstanders both use their Omniguide, which turns the radiation pattern into a slightly forward-firing hemisphere. It has wonderful dispersion, which--along with a well-designed crossover--eliminates any nasality.