I’m thinking of doing just that too, only in my case I am fortunate to have two bathrooms, so I would make the “guest” bathroom into a loo/ washbasin/ shower/ laundry. I already keep the ironing board and the ironing basket in there, so it looks a bit like a laundry room anyway. I think the major problem, as you indicate, would be ventilation, but a good ventilation engineer should be able to advise. Or a good electrician who has experience in ventilation. The second problem would be choosing the appropriate tumble dryer, as some need outside ventilation. My daughter has a condenser, which means emptying a tank of water after every load. This might be the best for you, but again, a good electrician should be able to advise. My son-in-law law, who is a bathroom fitter, has assured me it could be done (he subcontracts the electrics, but has a good knowledge himself from working with them.) My daughter’s apartment in Amsterdam had a bathroom/ laundry room. It was a good use of space, as yours will be. Good luck!