Aggregator API Developer Needed -- 2

I'm in need of an experienced API developer(s) to assist with integrating our platform with multiple external systems in USA. Budget is in the project so don't bid with placeholder budget.. Put a range in minimum somewhere.

Plaid API aggregates with multiple finance systems (banks mainly) and their investment aggregation didn't work for me.

Since Plaid API didn't work for me I am thinking we will have our own APIs to integrate to any investment banks/ brokers like E*Trade, TD Ameritrade (now part of Schwab), Vanguard, Fidelity, Robinhood , Interactive Brokers, Merill Edge and many more.
See: https://plaid.com/products/investments/
Our APIs allow users to:
1) Get Holdings/ Positions (stocks, bonds, mutual funds, options, ETFs, etc.). We will pass institute name, account # or login/password,
2) Get Transactions (Dividend Paid, Bough, Interest Charged, Fees, Sold, Bought positions etc.) for a given account/ institute.

We will publish two things:
1) In order to work with us as a broker/ investment what we need at minimum - certification steps
2) APIs for anyone to work with that broker through our APIs

Our Approach will be:
(1) Identify 3-5 brokers/investment houses (I guess using APIs) and find out how to suck above information from them>
(2) Write APIs for our customers
(3) In subsequent phases - expand support to many brokers/Account types.


Key Responsibilities:
- Developing APIs for integrating our system with more than 6 external platforms
- Ensuring smooth and seamless data flow

Ideal candidates should have:
- Proven experience in developing APIs
- A good understanding of data integration
- Experience working with financial systems/ brokerages to understand various investment vehicles one can get
- Different type of accounts / knowledge/ what is IRA or non-IRA for example.

Please message me with your relevant experience and how you can add value to our project.