i looked into this some years ago . it will never happen for one reason ...INSURANCE .. and that,s not all , who would take care of the bike between times when it,s not being used ? where would it be kept ? who would be responsible for buying and choosing consumables like tyres ? chain and sprockets , who would be responsible if one rider trashes the bike ? what if you arrive in europe for a tour on the bike and the previous rider failed to mention that the tyres are shot ? or the brake pads are badly worn or that they were flashed a dozen times by speed cameras in several different countries , meaning that the next unfortunate rider would be stopped by the police and made to explain himself in a foreign language ,fined or worse have the bike confiscated ! . as i said , i seriously looked into doing just this some years ago and it,s just too complicated and expensive to set up and maintain . i now understand why some bike rental places are so seemingly expensive !
go with a good rental company , that way all the paperwork and legalities are taken care of, and you can just get on with enjoying the scenery .