There was a time when "his" was used for "its:" "Love alone his love is keeping;" "the salt shall lose his flavor." I think we should extend this usage and use "his" as the sole possessive singular adjective. It would solve two problems. The apostrophe s usually denotes possessive singular, which is why "its" and "it's" are confused. "His" and "it's" would be less confusing. Also you wouldn't have people using "their" or worse "his or her" for "his." I would appreciate it if some mudcat from Northern England would initiate this change, for people from this region are remarkably successful in making changes to our language. Surely you will grant that changing "heighth" to height" was even wackier than what I propose. No one would countenance widt breadt dept girt ...