I don't see much benefit in changing sides of the road. There is ample choice in new RHD vehicles. Cars in Australia seem to be significantly cheaper yet they have also RHD. That says to me that factors other than (LHD/RHD) are more important.
There is a very likely high human cost in accidents - I'm thinking mainly of head-on open road accidents here.
The costs of such a changeover would be vast. Signs, road markings, angle parks, every motorway ramp, some traffic lights, traffic islands, some level crossings the list goes on.
It would seem impossible to avoid a long and messy transition. After we made such a transition we would end up with a fleet of vehicles with the driving position on the wrong side.