< doesn't cordovasim.eclipse require cordovasim anyways? But sure - for this kind of cleanup it should be in a different plugin.
So, should I refactor this part with delimiter duplication by placing it only in one class?
< With respect to parameters than it is normal practice to quote things with spaces.
Sure, I do this in one place for both BrowserSim & CordovaSim - see argumentsListToString method in PreferencesUtil. 
<If a user runs this cordovasim or browsersim standalone he would need to type out this long constant too ?
Nope he wouldn't. He would type parameters just like before. This delimiter will be used only for changing browser engine swt webkit -> javaFx and vice verse. User will not be aware of it