There are two dimensions here: how members are graded and how my votes are cast
Grading members
I'd suggest that if I abstain and my Congresss member does not, that that counts as a half point against my rep/Senator rather than a full point
Determining how my votes are cast
If I have a member of Congress who doesn't vote on a bill, I (personally) don't want that to count as an abstention for me. It's too ambiguous - it covers all reasons that they don't vote. I suggest treating it like a regular proxy when they don't cast a vote.
I'd really like this to apply retroactively, as my member of Congress (who actually represents me pretty well) has been heavily penalized by this