I love it, and are considering this myself which is why I can offer an insight to installation. Yours is luckily freestanding, however I would install this central to the long part of your L and enclose it within cabinetry, actually yours is Likely to just be faced with fake doors and no carcass behind, still a place to utilize storing buckets or baskets, even laundry powder, just not a standard cupboard. I would then actually install a stone benchtop making this technically undermount trough. You would still have the practical size and aesthetic impact this concrete relic has to contribute. Only, with the bench top area to make it a useable space.

the reno programs i've seen show a very unrealistic idea of how quick and easy it's supposed to be... your rooms are so generous that re-arranging the fridge, extra storage and seating at the kitchen bench is easy and i've attached an idea for a walk in pantry for your consideration?? BTW i meant the actual structure of the floor, concrete or timber framed in case you want to try the stove or sink away from the outside walls. I'm glad you like the ensuite and wiw and happy to attempt any variations but, much as i like planning kitchens and bathrooms, i suggest you need to confirm the overall construction, especially the roof, before finalising ideas about the internal fit out eg the yellow gable roof in my last suggestion would probably cost as much extra as the bathroom fittings and neither can be changed easily. The new kitchen cupboards would probably cost as much as the plumbing, electrican and windows but maybe the new kitchen could wait...so its' best to decide where you need to economise before you commit

As C R says, you will need to check with council or relative authority before planting into one of their assets. There's a lot of subsurface assets in a bio retention systems (drainage not to mention the soil itself) which they may not be happy about you disrupting. They will also be able to advise of the preferred species for your area and taking into account the filtration media depth (you need min 800mm media depth for tree planting in a bio swale or retention system).

If you are thinking of selling soon then avoiding having less than comparable houses have does make sense. On the other hand I agree with Dr Retro that other factors are more important and no-one is going to make a decision based solely on number of ensuite basins. Personally I'd be fine with one basin and I definitely want some bench space. If the bench is a generous size I might appreciate the space to install a second basin in the future so offsetting the single basin if you can seems a good idea. The thing that would put me off is if there are 2 basins which are crowded. I have seen layouts where I can't imagine two people trying to do something at the same time without constantly bumping each other or one person has to squeeze past the other to access the basin or lean against the wc or almost climb in the shower to use the basin or there is no surface space to put anything down on or wall space left for towel rails. When I see that I immediately start tallying up the work and cost involved in ripping the double vanity out.