1) Scaling and the success of the scaling process. As I am based in Lithuania, so I see that they (both Spectro and Bankera) started a hiring spree. As any user of a big web platforms you will know that maintaining a growing platform will cost more in terms of customer support, various web resources etc. So it would be reassuring to get a report on how is the entire project coping with the increased number of customers and complexity.
2) Burn rate. As this venture is using what it collects to finance itself when growing and pooling resources to start the bank it would give more confidence to see that it uses it's resources efficiently.
3) Regulation. As the entire venture will go into an area where regulation is important and elaborate (if you read the whitepaper you will see that Bankera will get into lending and investment banking), so when the regulatory enviroment will be chosen (If I understand correctly it will be EU , but the decission will be taken on where exactly - with Lithuania, Estonia, Malta, and the tax-havens as options) then some more detailed document on how this decision changes the project would be a positive sign.
4) More detailed timetables on the trading plaform. The sooner the better, as the coinholders will experience a bump in their returns.
The whitepaper explicitly states that they promise nothing in transparency on the abovementioned points. But IMHO they would help as honesty at this point in time is the best policy.
The entire crypto entering the traditional and investment banking idea is interesting, and could be wildly successful.
If this machine is up and running I do see a future where the Bankera will at some point in the future buy out the coins and will become a successful bank.
Thank you for the feedback.