This thread seems to be a bit null and void. State ownership and strategic airport planning was considered in the 1960's, but only those deemed important nationally were retained under state control (BAA), the rest were left to their own devices.
Surely, as more of the regional airports are taken over by the private sector, it is these owners which will decide the direction these airports will go in. Some may grow and prosper while others will go to the wall, but I would bet that the ones that dont last are the ones that can be truly classed as 'marginal'.