Make score available as pseudo field in Function Queries

Spinoff from Slack thread https://the-asf.slack.com/archives/CEKUCUNE9/p1606911042386800

I'm caclulating a custom score to return as a field based on a function query, i.e.
fl=udid,score,myScore:div(log(div(query($q),360.85104)),div(log(div(7.6316385,360.85104)),-3))
This turns out to be very expensive due to the query($q) part. The score is already present when running this function, so is there a function that will access the score directly, e.g. score() instead of running a query($q)? Using plain score does not work as it is not a literal field.

dsmiley suggested that making score a pseudo field, returning the score of the current hit, would be fairly easy now.