The gigantic challenge right now is allowing the system I wrote to fit nicely with the multiplayer code. I had rewritten a portion of the lock code to be a bit more elegant and allow for more interesting lock types. However, the engine communicates lock information via packets in multiplayer in order to verify who is firing what at who.
If you have multiple aspect seekers, the process that's responsible for running the gameplay needs to know which targets those seekers are locked on to so people can't just spawn a bunch of weapon fire packets unfairly set to home in on a player. I have to make sure the engine somehow sends network lock data for each and every seeker. It's doable but tricky.
A good question is why even bother getting this working in multiplayer and just make it a singleplayer feature. Well, then that would mean that I have to develop and maintain two different codepaths for the lock code and the lock-weapon interaction. It's more overhead, could introduce a whole slew of bugs, and just messy if someone else needs to do modifications to the weapon and locking code. Plus, this isn't just for multilock missiles, this work is also for a bunch of new locking behavior I'm planning on implementing.