I have found this annoying too. However I have just had a quick look at the editor source code and it looks like there is actually a option to turn this off already; at least in 4.8/Master branch.
In the baseEditorUserSettings.ini should be bAutomaticallyHotReloadNewClasses = true. Changing this to false should stop the auto recompiling when adding new classes; Except for the first class that you add to a Blueprint only project. I haven’t actually tested it yet, but from the source code for the master branch, it certainly should work. Though I have no idea if it is in older versions.
Turning it off will stop new classes showing up in the content browser until after you do recompile, and a warning to that effect will be displayed when you add new classes. It will also stop visual studio being automatically opened to that class, and instead the Dialog asking if you want to edit the code should be shown. Which I think should be the shown even if you have it automatically recompiling the classes. Especially now with the new experimental code editor plugin. It has been annoying when I’ve been testing that out, that visual studio is still opened after I add each new class.