I've just finished building brand new house and I put standard domestic
Hot Water heater with tank. Now I see that Takagi and other
manufacturers makes tankless water heaters and they are not that much
more expensive than standard domestic ones. My question is, if I ever
decide to get rid of domestic ones can I put Takagi tankless water
heater instead eventhou I was told It will be bloody expensive because
my mecanical room is not on outside wall, it is in the middle of the
house. Does that make any sense to you?

Thanks!