The ability to heal pets can be added in the code for sure - I did it for my little guildwars server shortly after the original GW died. I'm not sure if the pets db table is still used or not(honestly haven't even bothered to look at pets yet for Evertorn), but you may be able to do it there as well if it's still used.
If you're playing on someone elses server, try to contact them and get them to take a look.
