There is a muse upgrade available in Rimward (page 199) for "Titanian Muses":
Titanian muses commonly have the following skills: Academics: History 60, Academics: Political Science 60, Interest: Parliamentary Procedure 60, and Profession: Law 60. A common muse upgrade, the Plurality package, contains all of these skills and may be acquired from several Titanian microcorps at a cost of [Moderate].
Interestingly, that source book also describes a custom Jovian muse called a "minder", but there are no stats, so perhaps that is just a standard morph and the extra functionality is roleplayed if necessary.
Transhuman (page 168) indirectly warns against improving the skills and aptitudes of a muse:
Obviously the muse should not be a crutch that always has perfect advice. They have significant limitations, namely their low aptitudes and small selection of skills. Gamemasters should only use muses as a way to advise players when they are not taking certain options or clues that they should know into account.
In roleplaying terms, you could say muses have a specific hardware specification and therefore cannot physically raise their skills or aptitudes above this level. Muses are also designed to perform a specific function, effectively act as a Siri and companionship, so their base set of skills makes sense. I seriously question why a player would want to make a custom muse, other than to try and game the system.
It will also get to an "uncanny valley" level if you do so - with sufficiently high aptitudes, is the muse sentient?
That's not to stop you creating a souped-up muse for an NPC enemy, for an adventure exploring the limits of muse technology. My advice would be to not afford that ability to the players.