This would be a nice idea as the P2P instancing can be really bad at times. However, I'm sure it would never fly due to increased costs on their part. For them to do it, there would probably have to a monthly charge to play. Not something I, or others, really want to deal with.
Also, if were going "Open Only" then they need to add some king of PvP flag system like WoW has. You are never going to win over people to Open without it.
Finally, they would also have to fix issues that the other modes existence actually solves - e.g. being able to switch modes so that you can land because all the landing pads are being hogged/blocked at a station in Open. I suppose they could have multiple instances, that you can choose from (until filled), much like STO and other games have done. Though that would undo some of the reason for this Open only/server based system you propose.
It would also be completely bonkers because at any give time, > 95% of all the players in game are likely alone or with 1-2 other players in an instance and a dedicated server would be a complete waste.
A game this size is designed for a p2p network architecture and anything else doesn't make any sense at all.