plusminus, I'll try to address your concerns about the use of GF/GA ratios.
First, my adjusted plusminus metric does not use the player's onice GF/GA ratio (RON) in the calculations. Only the difference is used, as in regular plusminus.
The ROFF ratio is used to calculate the team adjustment component, in conjunction with the sum of GA and GF. So the adjustment scales with the number of GF and GA, just as with regular plusminus
I really don't think your concerns about the use of ratios apply to this metric. The ratios are useful for a quick overview of the on/off ice relationship of the player and team, but are incomplete without a measure of quantity. Adjusted plusminus includes a measure of quantity.
