Looks like plus500 do accept bitcoin deposits
How about a modern bitcoin stats status board? Keep track of market caps, trading volume, price, transactions, etc. displayed in a beautiful real time ui? So you could have a monitor to display in your office with all the stats you need on it?
We have coinmarketcap, for monitoring such stats.
I think mostly, site service related bitcoin, especially digitally, is already there, just what can I see is the developing itself, for example digital marketplace, there are pretty a lot, but lack of development, mostly dead.
And I think if you want to create an awesome project, better to research a problem around you, what people needs and develop it with good development.