To me it seems both kaynd and sinbad ideas will result in the same thing (i.e. spec racing) but with kaynd's version you could see more variations were with sinbad's version we will be lumped with the developers interpretation.
I personally think it is better to leave it to the community to design and implement spec serries - although that doesn't guarantee good results as you can't predict which serries will become popular and just because it's popular doesn't mean its good
. Where with fixed spec serries by the developers there is also no guarantee that it will be good but as with most things implemented it's likely to be ironed out in test patches - a good point is that the spec serries will be forced so the takeup of the serries is assured - the bad is that there is less opportunity for variaty and also it will require time and effort on the developers behalf to maintain the spec serries (as with any physics change they will need refreshing, etc)
So all in all I still think that the best solution is to have full adjustability but allow servers to set setup restrictions and a default setup. (i.e. let the community design, implement and maintain spec serries racing)