Is there a reasonable suit preference signal on this lead?
The basic idea is reasonable but unpopular, perhaps justifiably so.

The main problem with using SP here is that declarer may hold no stopper in the suit. East needs a way to encourage with Qxx.

Some top pairs never the less agree to use SP extensively on the opening lead. I have not used this method, but having three suits in play seems impractical. East's card will often be difficult to read, and usually dummy will furnish enough of a clue to rule out one of the side suits.

If you do use attitude here, as I do, I suggest following the suggestion of the late Helge Vinje from his New Ideas in Defensive Play in Bridge. He used upside down attitude and would discourage with the J from Jxx. Now when East plays a high card lower than the J West may be well placed to continue with a low card at trick two.