SUMMARY: After extensive review of available services and providers, we decided to hire
Mobidax.io.
I don't want to knock most of the posts in this thread, but everyone I've talked to here, and you know who you are, were offering sub-par applications, where unable to clearly define architecture or explain what would be used to manage exchange wallets and interact with Blockchains. Prices where readily available and to me that is a HUGE warning sign that leads to unmanageable software.
Others were White Label solutions and code ownership is not an option, but as I state in the original post, ability to own the source code for the application is a business requirement.
The team we went with are building our application using Flutter (
https://flutter.dev) for our Front-end, GraphQL (
https://graphql.org) for API Management and opensource Back-end Peatio - Wallet/Blockchain Management (
https://github.com/openware/peatio) and Barong - KYC + Auth0 (
https://github.com/openware/barong) in a micro-service infrastructure deployed on Docker Swarm (Later Kubernetes - for hybrid cloud/baremetal solution).
Thank you everyone for the advice and for helping us find the solution we were looking for!