So we went ahead and bought that water rowing machine. It's no Concept 2 but it actually works pretty well - haven't had a workout on it yet (my wife is currently using it) but I've rowed 500 m just for the feel and it is actually pretty good. It's a tad expensive but the Concept 2 is as well so it's alright. The good thing about it is that it doesn't look out of place in our bedroom and it's actually quite small when standing upright. I'll need to try it properly in order to talk more about it - stay tuned.
Also got permission to buy some squat racks - the only demand is that they are small and easily stowed away when not in use. I think the ones that I showed a picture of previously might fit our closet. Once I get those, we have a nice home gym with two kettlebells (20 kg and 12 kg), a barbell (up to 60 kg), a rowing machine and a dumbbell (up to 10 kg). Along with running outside that should be enough for now.