The plugin does not interface with Bitstamp.
Everything is possible with enough work, but the information you posted does not really help. And it does not address my point that the plugin should work with all coin adapters, not just one wallet or another.
The way to support fiat would be as I described in my previous post, but it does not make sense at the moment since the trading platform is not yet released.
Once the trading platform is released and is stable, there could be maybe a PayPal adapter or or an adapter that brings in any other fiat payments processor. That could work. But with my current work load I do not realistically see this happening in 2018 unless someone else does it.
This is why I have explained in the FAQ that I will not support fiat. It is a common request, and I do not want people to erroneously expect that I will release a fiat adapter any time soon.
Hope this answers your question.