Could we trade with institutional or bank using MT5 via API ? How about other country regulation like FCA or ASIC or FINMA ?
FINMA is Switzerland's regulator, so you are OK there.
ASIC and the UK FCA are good. What worries me about both ASIC and FCA is that they do sometimes let brokers get away with some questionable activity. FINMA and the US regulators generally crush bad behavior more thoroughly.
No matter what, make very very sure which branch of the broker you are dealing with. Just because the broker is registered with the NFA or FINMA doesn't mean you are protected. Many brokers are groups of companies. Certain clients are under tight regulations and others are under a branch that's barely regulated or even fully unregulated.
It's possible that some institutional account offerings might include access to MT4/5. For the amount of money you are talking about trading, you should be able to easily hire a coder to translate orders from a demo account on MT directly to the real account's trading interface. You would just use the demo for a price feed and the look/feel of the MT order interface.
Another option is to trade currencies on a regulated options/futures exchange (be aware that this is completely unrelated to binary options). Sive talks about that here:
An exchange removes the availability of many sorts of broker abuse. Every tick is the same for all traders on the exchange no matter which broker they use. Every bid and every offer is also on display.