Since, Wise & Revolut have been mentioned quite a bit and I'm an ex-Revolut & ex-Wise engineer where I built a lot of the FX infrastructure so I'll throw in my 2c.
My assumption of what you & Neeraj are doing based on your backgrounds:
You've decided to build a smart order router for retail FX hence the slow transfers because you need to wait for the spot order to settle T+2.
Story at Wise
Funnily enough Wise started in the early days with a fixed fee of £1!
Since all Wise did was match orders between customers so no money was actually moving borders hence no need for conversion or transfer fees etc.
But that fixed fee model was quickly scrapped when Wise started making the market between customers and improving the product experience by introducing rate locks (hedging costs), instant transfers (buffer costs) and actually started considering all the other cogs that go into making an international FX payment.
But there's one significant cost of high value transfers that's been a struggle for both Wise & Revolut to bring down even at scale:
The transaction monitoring, AML & support costs of high value transfers - a single high value transfer can easily cost £3 - £150 for all the due diligence needed to get it done.
If you're going to keep the product fixed fee - this is where you'll need to focus in terms of innovation.
The Story at Revolut
Revolut has an Unlimited Zero Mark up FX with a single free SWIFT transfer (every additional international transfer is capped at £5) on the £6.99 premium plan.
But international payments is relatively a recent addition. The vast majority of the time when people are sending money to each other on Revolut, it's a Revolut-to-Revolut or Revolut to local own bank account payment.
Revolut's core strategy is to be the everywhere wallet so that when you're sending money to your family member in Romania from the UK - you just do it as a Revolut to Revolut payment which is bit different to the gap you're trying to fill.
And, there's very little interest at Rev to deal with high value transfers because the AML, transaction monitoring and support costs are too prohibitive when transfers between users are free or capped at £5 for SWIFT payments.
Is there a market for this product?
A resounding YES.
This is something we realised at Wise - we weren't as competitive as we liked to be on high value transfers and even though they committed resources to improving this - in typical Wise fashion the progress is very slow.
Now I'm not convinced you'll stick at the £3 mark for long but there's definitely a large untapped market here.
I'm confident that you & Neeraj have what it takes to win in this market & will be rooting for you from the outside!
P.S. The app doesn't seem to be available in the UK app store?