As uwtartarus, yes, muses are just AIs and there are some rules, i think in transhuman, on how to upgrade a muse. And while nothing speaks against not using a standard muse - indeed, the books point out that some people use forks of themselves as muses - a security AI might not be very good at that whole "Organising your life" thing that a muse is used for. So your player can just grab another AI. Your Mesh inserts are afaik capable of running multiple AIs with no issue. A ghostrider is only required if you want another Ego in your head, and an AI is not an AGI, which would require that.

There are no official rules for getting better AIs (to the best of my knowledge). The closest to something official was something mentioned in Rimward (p. 199), an upgrade package to your muse to give them political knowledge skills needed to function well in the Titanian Commonwealth culture. You could get 4 knowledge skills at 60 for the price of [Moderate]. Not just any skills, but some are broad skills such like history and political science. There was some player made rules around here somewhere about making your own AIs. Prices for AIs based upon their CP cost. I don't know where to find it at the moment. If I recall correctly, it started the AIs off with a base package of 10 aptitude points in every aptitude type, then you added skills and more aptitude points using CP. How much the AI would cost was determined by how much CP was used. 200 CP was [Moderate], 300 CP was [High], 400 CP was [Expensive]. Very common AIs (such as muses) or highly specialized (and thus limited use) AIs might have its price one step lower. Remember, these AIs are limited and therefore unable to have: aptitudes beyond 20, active skills beyond 40 (many are less than that), and knowledge skills beyond 90 (the max I've seen used is 80). You're not obligated to use all the CP, as some AIs use less, such as the Device AI which uses 155 CP. The numbers given are a rough guidelines for how capable an AI should be for its price range.

That's what I thought but I didn't have the books handy. Portable Server, 10 alpha forks running wirehead eidolons, commanding Guardian Angels equipped with all the heavy guns, much success!

well if its sunward vendor then the copy protection will kick in DW :P

Depends where you are most likely. Fresh Kills is a place you probably could, but it would be a lot less likely in a place with inner system memeplexes more than astrography. It is worth noting that while infomorphs jamming bots looks really powerful EMP weapons can disrupt the connection at longer ranges, and intentional jamming can completely cut them off, and requires nothing more than an ecto or mesh inserts. Jamming is insanely strong. DDoSing the server is also effective, but requires more planning.

Well, Muses kinda have all the skill softs including knowledge ones. Muses can kidna assist you on nearly every roll.