The only way you'll get a better spectacle on track is if you introduce MORE variables, not less. The FIA have contributed to the stale show by insisting that all cars are essentially identical (v8s .. even with the bore centres defined, aero regulations, electronics regulations etc.)
Now they've introduced a standard tyre (whereas I'd say the tyre war made 2006 the vintage it was) and next year they'll all have a standard ECU.
Allowing a free(r) rein in design WILL favour the rich teams but it will also allow a small but ingenious team to also have a good season when they discover some way of doing something different to the big teams but which gives an advantage at enough tracks.
I say there needs to be different design options available. For example a team should be allowed to run a 10 or 12 cylinder engine if they want. That's obviously thirstier and heavier than a 8-pot but it could make more BHP (if the FIA got rid of their imposed for 2006 rev limiter) so that will give it the edge at Monza, Indianapolis.. it'd be less good at Monaco, Hungary..
Teams should have the option to run a "light" car (say 550kg cf. 600kg) up to a certain number of times (3 or 4 races a season with some restrictions ... like no "light" car at Monaco). The trade-off should be that the light car can only be refuelled once per race, rather than 2 or 3 times. That'll make it nippy at certain points of the race but less nippy at others.
Some tracks would suit these different approaches, others won't .. the teams will also get it wrong from time to time, if the weather is variable or if they get stuck behind a "normal" or a "light" car at the wrong time.
So that introduces variation in speed between cars at different tracks or at different parts of a race.. So how to get past the slower car but not TOO easily (it shoudl still be possible to win in a slow car).
Tyres should be slick but brakes should be steel and smaller diameter than present. Electronics .. yadda, yadda... for the techies and the scrutineers!.. but the clutch and gearchange should be manual.
There should be 3 tyre manufacturers.
Pit stops must still be allowed.
They should put me in charge of the FIA!