I suppose this is similar to considering komi as just a more fine-grained form of handicap, and the rating system accounting for komi like that.
I think it’s even already the case on smaller boards. Although it seems to be broken for a long time already, a fix is in the pipeline: Proposal: Redesign small board komi and handicap. From there it seems a small step to include non-standard komi 19x19 games as ranked games.