I think the idea could be fun, but although I have over 400 potted plants, they are - for the vast majority at any rate - outside. I know there is someone else on these boards who has an oak tree in a pot, but cannot find the discussion thread when we spoke about it - but as it is outdoors it is excluded anyway.
You do see huge plants in places such as airports and shopping entres, which are, I assume looked after professionally - I guess these would be excluded as well? Driving through Belgium it is noticeable there that the days of the big houseplant is alive and well, maybe in other countries too? I see them less often here.
Are you looking at plants in peoples homes, using conservatory plants? This could exclude people with just the sort of plant in which I think you are interested. Will keep an eye on this thread and see where it goes.
I think the days of the giant aspidiatra, and sanservia (mother in laws tongue) are virtaully past. Probably people on the whole do not have the room for them in smaller homes, besides which central heating put paid to many of them over the years.