I also would like to see this change, but I have a hunch it would be rather difficult to implement, as the 3-tilde and 4-tilde signatures that we have now are a standard mediawiki feature. My default signature at Wikipedia is my Wikpedia ID, just as my Wikitree signature is my WikiTree ID.
At Wikipedia, I am known only by the alias I use as my ID, so the default works just fine. However, here on WikiTree I am known almost entirely by my name, so my ID is not an effective identifier. I sometimes go back and insert my name in the display field of signatures generated by the default here. I would appreciate it if the system could do that automatically.
While we are discussing signatures, I think it would be very nice if I could use tildes to sign the notes I add inside footnotes that are created with <ref> tags. I would sign more such notes if I could do so more easily.