Downsizing - What to keep and what to part with?

[cronv]

So currently sitting on my desk (42in by 24in) is a 40g Breeder, which takes up the entire desk. There is also a 5.5g above the 40g on a shelf. I'm getting a new desk which is 38in by 24in that has no shelves on the back compared to my current one that does.

Here's where I need some help:
I'd like to get rid of the 40g and free up some usable desk space. How should I go about that? Should I buy a different tank? Should I build a new tank? Should I make a long skinny one at the back of my desk or one to sit on the side?

Also, what fish should I keep and which ones should I rehome?
In 5.5g:
- 1 Male Betta (Keep)
- 5 Glowlight Tetras (Would like to keep)

In 40g:
- 10 Zebra Danios (Could live without)
- 6 Australian Rainbows (Could live without)
- 4 Cherry Barbs (Undecided)
- 2 Siamese Algae Eaters (Would like to keep)
- 2 German Blue Rams (Keep)
- 1 Dwarf Gourami (Already found a new home)

Here's kind of what I'm thinking, but this could change anytime:
- Purchase a shelf that could sit on desk or over that could house several small fish tank (5-10 gallons)
- Build a tank for the side of the desk (18 x 18 x 18)(about 25g) for a downsized community tank
- Betta and Glowlight Tetras in 10g on shelf
- German Rams in 10g?
- Danios, Barbs, SAE, and Gourami in 25g?

Please give me any ideas. I'm open to them all. Seriously, I've had some pretty crazy ones, so yours can't be that bad.

 

[cronv]

Here's a quick drawing of what I'm thinking, let me know. Also, this isn't quite to scale.

 

[Mebbid]

Is there a reason you can't just get a stand for the 40g and keep everything?

You also don't need to make a custom tank, they make cube tanks in a variety of sizes.