If you widen the slots for plain guts, you may very well experience buzzing - particularly from the nut - if you switch back to Oblis or steels. It will mean either having a new nut fitted to again allow buzz-free use of thinner gauge strings, or filling the enlarged slots of the current nut and re-filing new slots. I'd recommend the former, since you'll then have a nut you can use with your plain gut set, and another to use with thinner strings should the need arise to switch back and forth or if you'd just like to change it up once in a while. I've found bridge slots to be far more forgiving when using strings of different gauges, so that might never become an issue for you.
