Ok, this discussion is really good and it sounds like there is something going on in the murk of DC's mind at the minute
The thing is that you will never please all of the people all of the time, so the best thing to do is put some proposals together and put them to the vote (on here not the BRCA unless we do want to get them to autherise it is a national "B" series).
So what are the considerations that need thought? Well to my mind there are a few things (and many more that I haven't put down here).
1) F1/F2 drivers. I can understand that the idea is for the drivers who can't/don't want to get involved in the national series something else to compete in. That said if you start excluding anybody you will also start to exclude their mates they travel with etc etc etc etc.
I think that the best thing is to "discourage" rather than exclude, there are several ways of achieving that; same day as nationals, penalties for F1 drivers (say their times are multiplied by 110% so it moves them down the order ... if they are really 10% faster than the next guy nothing is going to stop them winning anyway!!).
Also the attraction of nationals for a lot of F3/4/5 racers IS to compete against the F1s and see how they compare or maybe just to watch them in awe and hopefully learn a thing or two.
I believe that the attempt to exclude certain groups of drivers from the old RRCi series helped finish the series off!
2) Dates; same dates as nationals will help discourage the F1 drivers (as they would certainly lose their F1 for the following year) but make it harder to organise as the big clubs tend to be run largely by accomplished racers/organisers (who would be at nationals) and also harder to get the media coverage.
3) MUST NOT damage regional entries! Some regions ARE over subscribed (West Mids for example) but most aren't ... if we dilute regional entries some clubs, even some regions, would start to struggle and may disappear. That is bad for the sport so must not be allowed to happen.
4) Rules; start putting motor limitations (as an example) and you will put people off as they will think "I've bought this motor to do regionals / BRCA meetings now I have to buy something else ... not interested". I think keeping the motors & cells as per the ones on the BRCA list helps encourage people to buy stuff they can use at other events and thus help allow them to cast their net wider. Maybe have a 2nd list of "acceptable" motors and cells that are cheaper / lower spec for the beginners etc. If you relax the rules what is stopping Joe Bloggs buying the Super-Dupa-Special monster motor and blitzing everybody who can't justify buying something they can only use for one even/series ... those people then get put off.
I think
control tires are an essential though to keep costs sensible, maybe even limit the number of sets used to prevent Mr Moneybags putting a fresh set on every run and nullifying the chances of Little Johny with his paper round budget. You want to keep the tire to a commonly used range to as a lot of people can then chose to 'use up what they have left over' from other events to further reduce costs.
I am also fairly sure that several of the tire suppliers would be happy to do a discounted deal for tires bought at events if asked nicely and given an incentive (like them being the only supplier for wet / dry tire choice).
I also think that the tire choice needs to be consistent for ALL rounds for the same reasons.
There is a lot to consider in my opinion, not knowing what DC is up to I can't comment but one thing is for sure ...
1/10th off-road is back with a bang and the numbers now support more than one national series