For space yes, but let's face it anything mechanical like that will have a shorter life and is bound to break sometime. Also watch out for awkward shapes and shit like that. Can be a pain if for instance you like doing behind the head tricep extensions with two hands.

For the cost, 1" bar dumb bells with collar locks would be about the cheapest. Buy a shit load of 10lb steel 1" plates and you can load each dumb bell like a barbell. Ofc buy some 5lb, 2.5lb and 1.25lb weights too so you can adjust em down to 2.5lb increments. 14" db bars should be able to hold about 100lbs, and the 18" db bars should be able to hold 150 or so each

That's what I plan to do. it is by far the cheapest option.

Bowflex actually has nice adjustable ones as well

A set? What do you mean? As in 2000 pounds of dumbbells... 10lb, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90? That'll cost quite a bit if you can't find a Craigslist deal.

If you're talking about adjustable 1" ones, that's fine... but it takes a long time to adjust those things.

I had a full dumbbell set (5lb all the way up to 50lbs in all increments). I bought it cheap, sold it for a profit. But, it took up a lot of space.

Powerblocks were I think $650 (Canadian) for 5-90lb adjustable.

i would be looking for a set that goes up to like 50s
then i would add later on when more weight is needed