Just not really sure, I don’t think WebFig sends too much data unencrypted and it uses Java, but I really don’t know how strong that encryption is.
http://forum.mikrotik.com/t/webfig-encryption-over-http-how-does-that-work/48712/1
If you trust the ISP’s and datalinks in between you go for it. I would at least make the external port different than 80 though to obfuscate (And in case you have an actual http server that needs that port).