Calculate Fatigue and From based on eFTP?

[R2Tom]

You probably can do that yourself with a custom field which overwrites original load
See there for more details

Allow users to choose alternatives to TSS

You can actually update the default activity training load from a custom activity field script. Return your custom value but also update the value on the activity: activity.icu_training_load = ... Then your custom calc will automatically show up on all the usual charts.