Adjustable encumbrance thresholds

[Former user]

Currently the Variant Encumbrance option uses a fixed formula based on STR and size to calculate encumbrance thresholds. Having an advanced option to alter the formula on a per-character basis would be really helpful for representing things like Goliath's Strong Build feature in the Encumbrance ruleset as a homebrew option; RAW doesn't really support this since it only increases max carry capacity, but doesn't scale Encumbrance thresholds at all.