To make the increase in expenditure for any stat increase at every point achieved rather than the highest attribute or current skill value.
For example, having 60 in all stats would make your FEP bar 810 (10+50*8). That's 1:1. You could bring it back to 1:8 and it would be at 60 (10+50*8/8) again but then you could have 800 str and nothing in others for far cheaper than balanced development which is cool. Glass Cannons anyone?
Of course, a ratio of progressing the ideal development expense rates is a matter of balance not concept but probably lies near the median. Likewise, how that affects the viability of development would be dependent on the foods and their value. Given that FEPs can be a fraction then the increment can be applied at each iteration.
It would seem to discourage 'rainbow FEPs" but let take a Second tier fighter's development in this system (STR CON AGI) There are clearly enough foods currently in the system to give you a nice handful of choices in food. Soloist? Add int. Raiding party? Add Cha. Crafters likewise become force to specialize. It doesn't create a huge array of 'classes' but it does allow classes to arise naturally from the more equipment that is added and the more function/value that is tied to currently combat useless stats.
I mean to suggest that this be applied to skills as well although I don't mean to suggest that it would comprehensively address the ease of alt LPing (nor do I think it either can or should be).
It would then be possible to apply the trad/change slider to FEP's by targeting the ratio.
In summary, the effect isn't to change the cost of development so much as institute a choice-driven development curve that makes every character a secret sauce based on the economical considerations any player of any level of development is forced to choose between rather than being a linear value.
The short end of the stick here will end up with the hermit who will be forced to develop and play even more alts than are currently required to solo end game.