+1 for not doing the snow version. (Even though that's the set I have for o Gauge).
You are far more into tinplate than I am Scott, but to me part of the attraction of the tinplate trains is the crisp smooth colors. If you did them totally white, I'm not sure how that might affect the overall look of the set.
Of course if that aspect isn't really important to you, it's your set, but you asked for opinions....
Nice job on the engine so far!
-Dave