ALOT of people with symptoms of UCTD and no definite diagnosis get treated....in fact it's definitely the way to go! All the CTDs are interconnected so most of the treatments are too. Obviously you don't want to be on steroids (the nasty Prednisone) before you have to but there are lots of other options like the Plaquenil.
Want you will need is a rheumy who's on your side and is prepared to treat the symptoms. It may take a few to find the right one, but there are some good ones out there!