What you are saying is absolutely true, but it misses part of my point. The Alliance certainly has the capability to develop it's own ships, that is not in question.
However, what I was getting at is that they do not have a unified navy, and the different navies of the member planets/systems are going to have different needs.Because they all need different things, there is no unified will to make any particular kind of ship. And navies aren't going to want to contribute to the development costs of a ship they don't need, but which their neighbor does need.
The Alliance does have a unified navy and member systems are obligated to provide an amount of ships to it based on their GDP actually. Said navy is under jurisdiction of the Council of Admirals, who can make initiatives without having to ask permission from other authorities within the Alliance. This is the reason why ranks don't exist.
How many times do we have to remind people of that? If we didn't have a naval structure, what difference does it make for systems to join in? That's literally the selling point of providing extra safety to them through unison without delving too deep into their sociopolitical affairs other than requesting that the human bill of rights is upheld.
Plus, if there is not specific need, then the Alioth shipyards could focus on developing even better multi-purpose ships. That means that all systems can use them according to their needs. Noone said that we want purely combat ships. In fact, most Alliance commanders would be happy if the Alliance was given exceptional trading and mining ships. But an exceptional mining ship would be combat capable by default, because mining needs a good power distributor and module distribution, so we're talking about multi-purpose once again.
Our navies already operate on pythons and annies, so I don't see how systems wouldn't enjoy other good multi-purpose ships.
Additionally, the Alliance does not need to coerce smaller systems to take part in the research and development budget. Due to Mahon's influence, the Alliance should currently be considered filthy rich.
There are no arguments that haven't been dealt with when it comes to why the Alliance has no ships. Those might have worked back when the game started, but the commanders and groups who loved the Alliance for what it is have worked their butts off to change it, there are no excuses left after all the achievements the Alliance has made.