Actually I setup the build system so that you can add a normal mod to the normal mods directory (even ones that are release-obfuscated should work) just for such purposes. ^.^
By default I set it up so that a runtime launch launches with only the mods marked runtime or compile in the dependencies list, the compileOnly are not launched with it. Any additional mods added to the ${PWD}/mods directory are also loaded as normal via forge, but with a transformation to de-obfuscate them on-load so they run with the dev build. Editing your code while it is running worked fine in my tests as well when I built that build system. 
Eclipse of course has a bug of not mapping image directories properly, I’m not an eclipse user and couldn’t figure it out (if anyone else does though…!), but intellij worked fine in all cases. So even if you use eclipse for normal dev’ing and intellij for edit-and-continue…