Retaining the weight only and only weighing in if it's part of the active FEP roll bar.
For example. Lets say I eat a dozen RoBs and get a bunch of AGI. Now I eat a bunch of piros and mussels. If the mussel gets on the bar it would put PSY in the running and ressurect the old weight of the RoB's that never put out a PSY. So i work on it by keeping PSY in the running with the Food I eat and when it scores the weight disapears.
This keeps the value of all FEPs consumed without changing any of the relative value of the foods. Players will feel less like the process is a gamble and be rewarded for investing in a varied diet.
It would still be a gamble where that cost and investment varies but it's kind of heartbreaking to spend a lot time developing the resources to have roll at bringing psy a little closer to par just disappear right down the drain for bad luck but bad rolls can still make a point expensive to attain without a sense of loss this way.