But a station for there already exists, improve the service if need be. Liverpool is the second busiest airport in the North of England, transport to it needs improving firstly in my opinion.
Improving the Liverpool to Manchester Airport service currently relies on using the Castlefield corridor. It should be obvious by now that this will not provide any significant increase in capacity: Castlefield needs a "bypass" and that means a tunnel.
As to Liverpool Airport, busy as it may be, the passenger numbers currently fall well short of those required to justify a heavy-rail link. Experience globally shows the numbers needed are in the region of 9-12 million per annum, Liverpool's total for 2024 was just over 5 million.
So do we wait who knows how long for those passenger numbers to grow sufficiently (and it might never happen) or do we look at alternatives. In the short-term that means buses, the question is where from. Even in the medium and long terms buses are still likely to be part of the solution.
Long before Manchester Airport gained its heavy-rail connection it had a dedicated express bus service from the city centre. The capacity may have been rather small in the grand scheme of things but it was well known thanks to effective marketing, reasonably well used and established the idea in the region that getting to the airport didn't have to rely on the private car or taxi.
This may primarily be a rail forum but when discussing wider issues of connectivity we should not dismiss the bus as somehow not being good enough. In some situations it can be the best option.