Crossing Alps and Oxygen - rules?

[Fuji Abound]

I assume you wouldnt consider this trip without good GPS. On that basis I am not sure where you think ATC might come in with vectors? Over the Alps unless above the MSA they are not going to give you vectors, and in any event they arent going to see cloud on their radar (as opposed to precipitation). As with any flight above the MSA and IF in CAS you could request x degrees left or right for weather but the request is based on your visual perception of the weather ahead, or, if fitted, the weather information in the cockpit. To be frank at the point at which you start requesting vectors around weather unless you are very comfortable with what you are doing you might well do better with another plan (like turning back) because certainly I find when ever you start requesting vectors around weather there is a very good chance you will end up in IMC for a period of time. Once in IMC over the ALPs what are you going to do, even with ATC's help? You could ask for a climb, but you might not achieve VMC on top before exhausting your aircraft's performance, and you could ask for turns, but neither you or ATC will have much idea whether this is likely to take you out of the weather. Of course, what you cant do is ask for a descent which is often a good get out of trouble solution where the MSA is much lower and/or where you know there is VMC below. If you elected to stay in IMC for however long it took aside for the icing risk which is very real, you cant expect ATC to vector you "out of trouble". As a last resort it could be an option, but you definitely should not have got yourself into that situation in the first place unless you were also "happy" to take responsibility for your own navigation including diversions and for some unexpected reason (like dual GPS failures) things haven't gone well!

With apologies, I am not trying to teach you to suck eggs, or to bang on about IMC, but IMC above the Alps is really not a good idea and should be avoided at almost all cost unless you are very certain about your instrument flying and the aircraft's capability. In short unless you are very certain, the trip should be an assured VMC day and if it doesn't go to plan for any reason the old adage of turning back or diverting is a good one.