It’s impossible to have a plug-in system in an editor that fix those problems, and if you really wanted achieve one you’d have to put more thought into it than into Panda itself. If you didn’t then no two plug-ins would be compatible.
There’s a reason every game has its own editor, really. Every RTS game comes with it’s own editor for example. Can you imagine an universal editor that would work for more than two RTS games? Impossible. Take a look at the software applications industry, we have professional applications for everything, modeling, drawing, ides, we even have applications for the most specific and silly tasks like texture wrapping or asset management, but where are the universal scene editors being used by big studios for any game? There are none. I know there are some scene editors suited to particular engines like ogre3d but they could only be used for incredibly boring concepts.
In fact it wouldn’t work with almost any genre.
RTS? Nop.
Graphics adventure (extinct)? Nop.
Arcade? Nop.
Sport simulation? Nop.
MMO? Nop.
So that only leaves us with load-per-level 3d scenario games. But it still doesn’t work for most of them unless they are very small. For example if your game is multiplayer you are gonna want to have a BSP and visibility zones because you don’t want maphacks to be possible. This would need to be integral part of the editor and suited to your needs. Just an example, there are a million reasons you need your own formats when you have a complex game. The most important being that the loadable levels model is obsolete and now you want things to be seamless, doing a generic editor at this point is like embracing the 90’s. You now want to design game experiences around your networking infrastructure. Also scenarios need to be dynamic which means procedural content, which is incompatible with a generic editor, plug-ins or not because in order to have an editor you need to have some assumptions about some things that you may want to generate procedurally. This would be a piece of cake if instead of an editor you’d have a series of facilities to roll your own. But the other way around, generic editor with plug-ins it’s impossible, or it would have been done by now.