The Tragan Credit Union is an Imperial themed CU. In case you couldn't tell by my epic render, thats a statue of Emperor Tragan on top. Its also a third building to match the Hall of Bounty and Prestige Academy's architecture.
The TCU has two functions- Gold Banking and Nanopod CD (Certificate of Deposit)
Gold Banking 
For gold banking, simply deposit any amount of gold you wish to save for later.
Gold in the bank matures at a rate of 0.1% interest weekly, with a weekly timer counting down to maturity each week.
You can withdraw your gold whenever you want, but only collected interest remains if you leave it in until the weekly cycle hits.
Upgrading the TCU adds 0.1% interest, up to a maximum of 1% int. each week at level 10.
Nanopod CD 
Nanopod CDs are a good way to get Nanopods for free but since Nanopods are rare, you're not going to have Sleesh Squeesh Dave's Morgan's House Exclusion zone using this.
The way it works is simple-
You deposit a number of Nanopods into the bank, with a minimum of 50.
After a long period of time, maybe about 4 weeks(?), you get 5% of what you deposited into the CD.
You could withdraw the nanopods at any time, but doing so before the CD matures will not net you any interest.
Upgrading the TCU adds 0.5% interest to Nanopod CDs.
Why use this building?
As mentioned before, we really need a third building to match the Prestigous Academy.
But most importantly, it would give players an incentive to contemplate how they want to use Nanopods. They must consider- Should I spend them now for a boost, or save them and earn a few more? This could be the difference between an M10 and another unit, or a store vs Adv Resource.
I see this building being unlocked around level 20 or 30 because thats when the game gets hard and nano decisions become serious.
And again, the numbers might need to be tweaked and even capped, but an idea like this could be helpful