As a Croc keeper, I'll give insight the best I can.
The size enclosures you're thinking about building should be double by probably half...length and width wise anyway. You're going to need expansive enclosures, for each specimen. Keeping them together 100% of the time is not an option and you'll end up with a dead Croc.
I know the few people, in the US, that have pairs and are able to breed their pairs, to introduce CBB babies. But, due to ethical issues, most don't do it. There are to many people out there that would buy them, not knowing anything about them. This particular species cannot just hurt you...they can kill you. The St Louis Zoo shut down their Croc display, after one of their keepers was almost killed.
They are not a "handable" species...trust me. When I first got mine, I thought he was manageable. After having him for some time, now, I know he is not handable.
I'm not normally one of those guys that grills members, when they say they want something, but out of safety for not only you/friends/family but also the future pairing, but what experiance do you have, in keeping large Varanus?
The absolute best advice you're gonna be given, is to join this site...
http://www.varanus.nl/
Fair warning, tho. This site is filled with scientists, biologists, zoologists, very long time keepers, etc. It is a no nonsense forum, so be respectful, know that whatever advice/info you get, etc. is for your benefit and the benefit of any animal you may be purchasing.
Jump on there, join up and post this topic. You won't find better information, anywhere.