The W.4 was actually based on the Albatros D.1 airframe, so you would need to start with the Roden kit in 1/32 (or the D.II, as they are essentially the same). The bad news is that you would probably need two kits, since the wingspan of the W.4 was lengthened over that of the D.1 by, if I recall, about 3-4 feet. I suppose you could build your own wings, but it might be easier to extend them by grafting together the wings from two kits. You'll want to find a copy of the Windsock Mini Datafle for the W.4. I have naval hex decals in 1/32 for the W.4 that I ordered from Doug Bauman. You'll need to scratch the floats and a new larger horizontal stabilizer if memory serves, but that shouldn't be too hard.
I'm torn between going ahead with such a conversion next year some time, or just waiting to see if WNW or someone else does the W.4. I have so many great WNW kits to keep me busy while I wait!

I really do like the W.4 though, and want one in 1/32.
Good luck with your effort.
Regards,
Bob