It seems to me that your ability to do all those things in a year depends on how reasonable each is for you. If they are all the sort of thing where you just need to sharpen up in each discipline then sure, but if any one objective is a big reach that you need to improve significantly for then you should probably take a solid 6 months or more to focus on getting ready for it and accept that you need to sideline the other sports significantly.
The other question is time and energy. If you were in good enough climbing/endurance shape to give the B-C-in-a-day a run last year but you had to take 6 months off of any serious climbing because of work and you know you’ll be pulling 60+ hr weeks in the office the rest of the year with just short weekend trips here and there, then that may pose a problem. But if you live out of your van or work a flexible schedule and will be spending a large part of this year training for and doing these sports then its probably not a big deal to do all these things.
Assuming these are all reasonable objectives and you have the time/energy to get after it consistently I would do skiing in the spring, climbing in summer and running in the fall/early winter. Think of your B goals as workouts that can prep you for your A goals. Spend the Fall running and doing general strength twice a week; if you climb just do some casual laps at the gym or crag with friends, include a little hangboarding with your strength sessions. Do your 50k at the end of the fall, maybe travel to some area warmer and drier like near Moab or Bishop or Vegas for the race and then spend a few days after the race cragging as your legs recover. Come home take a down week and get right into winter ski training, go ski tour weekly instead of a long run, you’re still running on some work days when you can’t make it to the slopes, maybe now you’re doing Max Strength or even Muscular Endurance work and you join friends at the rock gym or crag once a week for a stack of pitches or some ARCing. As spring comes around you’re ski touring longer volcano objectives on the weekends and doing ME arm days and bouldering sessions during the week while the legs recover. You hit Rainier in May every weekend, if the weather sucks you skin some laps lower down and then bust over to Tieton for some cragging so as not to overtax yourself in case next weekend is perfect. You hit that good weather/partner weekend and send Lib Ridge, then take a down week and go cragging at Index. Now its rock season, you’re still running most work days but its pretty chill and bouldering/cragging 1-2 of those work days, weekend trips are now WA Pass or Enchantments, as with the skimo you have a series of B and C goals that you progress through to meet your volume and work on your skills. Late July or early August you set a new onsight best on one of these days and then rest up for a couple weeks before heading to the Bugs for that B-C-in-a-day. After that you use your airmiles and any vacation you miraculously have left to take your girlfriend to Hawaii and do ABSOLUTELY NOTHING besides chill on the beach (preferably for a month).
You mentioned 40 hr weeks. Yeah, sure that’s possible if you have a huge base and are well rested but don’t expect to do that week after week, especially setting new onsight bests too. Basically to pull this off you need to have a long build-up of general fitness and then have each of the goals be easy enough that they don’t require a serious peak or over-reaching of your energy reserves, otherwise you’re done and need to start the buildup over again. If any of your goals are a “wow this will be so much harder/bigger than anything I’ve ever done” then pick one for the year, only if all of them are a confident “I just need to make sure I’m in good shape for that trip” is it reasonable.