By all means a doublet, cut from the same tartan as your kilt, is perfectly acceptable and, indeed, desirable. To my mind's eye this style works best with a very traditional doublet (Sheriffmuir, regulation doublet, Dress Argyll, or similar) than it does with the ubiquitous Prince Charlie coatee. Our very own JSFMACJR (Sandy MacLean) often wears a tartan doublet and looks smashing. Perhaps he can be encouraged to join in the discussion.