I think it would be extremely difficult to create a platform to replace what the brokers or software vendors already supply. How would you fund the development, marketing and future support costs? Plus maintaining such a system would be a large ongoing effort due to constantly changing regulations, new security types (such as crypto), etc.
I believe your best bet would be a system that could work in conjunction with existing platforms to supply features that current platforms do not support.
I believe your best bet would be a system that could work in conjunction with existing platforms to supply features that current platforms do not support.