I like the regional fly-ins, but they lack the clout of the big rally. Perhaps a good way to spread the risk would be to make it a biennial event, with a big rally one year, followed by regionals the next, and so on?
The things I really miss about the single rally are (in no particular order) ...
1. Homebuilders tent.
2. Flea market.
3. Conference tent and interesting speakers.
4. Attractiveness of the event to foriegn visitors.
5. The incentive it creates to "get finished for the rally".
6. Meeting distant members.
These are things that the regionals just cannot do effectively. As a builder/flyer, the rally always acted as an incentive to try and get the project finished. Failing that, after I'd get home, it would "kick start" me to get on, having seen the results of others. Regionals do not seem to attract the numbers of foreign visitors, or members from areas far afield from your own. I loved the fact that you could strike up conversations in the beer tent with complete strangers speaking broken English (you Scot's, Welsh and Irish really could try harder ... most European's are easier to understand!

These things add up to the "need" for a focused large event, even if it's not annual. I don't profess to having much idea on what's involved in organising a large rally, and I'm sure it's ahuge undertaking. However, surely if the costs are more closely controlled as Brian suggests, and a good venue can be found, it MUST be worth the effort?
Ivan