A payment agent is definitely a legit structure if it acts really as an non-related payment agent.
If the payment agent is related and has the same UBO, tax authorities will quickly suspect that related︀ companies are being used to artificially reduce tax liabilities.
Volume doesn't mean you are on︁ the radar, there is a multitude of factors. Having a related company in a jurisdiction︂ as Malta or Cyprus is already one of them.
We have experience with this and︃ it's enough for EU tax authorities to see there is a related company in a︄ low tax jurisdiction to start a full blown investigation with raids, even the UBO does︅ not live in the EU. All the other tax authorities in Malta etc are contacted︆ and you shall provide all tax, bill, PL, bank transfer information of the past 7︇ years.
It might work and be useful in some setups, but it also draws a︈ lot of unnecessary attention. Malta company record is public and our businesses got into offshore︉ leaks. Which all drew authorities their attention.
I would personally not suggest anyone to create︊ and especially do business with a related company in a low tax jurisdiction if you︋ operate from an aggressive tax EU country or make sure you have setup the structure︌ well with a tax lawyer.