Cost of a Ultegra 6800 hydro disc groupset is about $900USD. Then there's the handlebars, and if you want carbon it's maybe $150. Stem-$50. Eleven-speed wheelset--...Unless you really, really want to do this and don't care about the cost, it's not going to be worthwhile. Save your money toward a second bike. If you do go for it, it'd likely cost you upwards of $1500. You can get a second real road bike with hydro disc brakes and 11-speed Ultegra for a few hundred more.