I'll probably have something more relevant to say when my experience level with Flixel has increased beyond "newcomer" level but here are my first reactions to the points you mentioned:
> pathfinding utility
Pathfinding solutions are very game dependant imo. A top down tile based game is very easy to represent as a graph and thus easily searchable with a standard Dijkstra or A*. But a lot of users of Flixel seem to be making Platformers. Pathfinding on a platformer type game might be a lot less straight forward. Are you looking for a generalized approach that's going to cover (almost) any type of game?
> some kind of line of sight or ray utility
Implementing that right now for a game flixel inspired me to start. Gonna post a playable something soonish. It'll be a pretty generic solution (would work well for platformers too) - if that's really something you'll want to integrate in flixel and you like how it turned out shoot me a message.
> some kind of magical light network thingy for online multiplayer
Flash doesn't support P2P (at least not yet) so you'll always need a server to connect to. Would you plan to develop a "Flixel Server" i.e. a application intended to run at the backend? Would it be something users have to host themselves? I think for most it's easier to hook up with a specialized portal like Nonoba and use their Api!
Speaking of magical light. I think it'd be cool if it were easier to implement lighting. Build in support for some kind of multipass rendering that combines layers based on the different BlendModes flash allready supports would be nice. This goes a bit in the direction of the Post-FX.