Alpine grading is an open game and frankly that's good. Alpine climbing is not so much about grading as it is about an experience and the intimate friendship you form when you are out there for days in an exposed environment as a team. When scouting for a suitable alpine route the first priority is to find a route that suites the current conditions. And not just the conditions effecting the route but also the decent. When that choice is made its time to get in to the details of the potential route and this is when grading becomes interesting to some extent. But this is when it gets slightly complicated. The traditional French alpine grades give an overall difficulty grade to a route, taking into consideration the length, difficulty, exposure and commitment-level (e.g. how hard it may be to retreat). These are, in increasing order:
PD: peu difficile (not very difficult)
AD: assez difficile (fairly difficult)
D: difficile (difficult)
TD: très difficile (very difficult)
ED1/2/3/4: extrêmement difficile (extremely difficult)
ABO: Abominablement difficile (Abominable) (Extremely difficult as well as being dangerous)
Often a + or a − is placed after the grade to indicate if a particular climb is at the lower or upper end of that grade (e.g. a climb slightly harder than "PD+" might be "AD−"). (source wikipedia)
This is giving you a general direction and a indication of what you will encounter on your accent. This system is how ever becoming less relevant as most modern routes are graded in 3 steps. 1st the serious grading in roman letter. Then the Ice grading indicating the level of technical difficulty with the symbol (WI). Then the M factor and this is where I think some innovation could be interesting to contemplate. The M grade is the grade for the mixed climbing and there exist two forms of M grading. The "sport" one and the alpine. In my experience the difference is huge between how a mixed section is grade on an alpine route and who it will match the grading on this not so new but still developing M sport routes equipped with bolts and belays etc. Given the almost non existing correlation between M alpine grading and M sport grading I think its all slightly confusing.
I would like to see a system for alpine mixed grading more like the British E grading system for alpine routes. Adding a factor indicating how serious the M climbing is just like on Trad climbing. Ignoring the E grading debate since all alpine climbing is on sight I think it would make huge sense to grade mixed alpine routes adding the E factor.
So it would look like this: V, WI 5, E5/M5.