If you can be bothered, return the ofo to as close to standard as you can.
Buyers like to think their secondhand purchase is not so inferior to new - anything that interferes with that feeling, such as accessories and tweaks, will reduce the bike's desirability.
Sounds daft, but a bike with £100 worth of fitted accessories will not sell as well as the same bike without those bits on it.
A bottle cage might not do any harm, but no one wants a bidon that, horror of horrors, someone else has slurped from, or - to them - someone else's smelly old saddle pack or trunk bag.
None of the above applies to the maker's spec for the bike, so standard is the way to go.