@Arkandel
For instance I might want to play a professional boxer but have no interest in having scenes around him sparring, working out, having actual fights
Then you shouldn't be playing a boxer.
Let me clarify: Most tabletop systems are about extraordinary people doing extraordinary things. If you are playing a boxer and your contribution to these extraordinary situations has nothing to do with boxing, then yes, I'm going to say you are playing your own character wrong at worst, that you don't get to increase your boxing skill at best.
Most tabletop systems don't award XP for downtime, and it's only the skill-based games I've seen that give GM the power to say "no" to spending. Really, the GM can say "no" to anything, but would be a complete jerk to do so.
Now, I'm talking in tabletop terms because the systems we're talking about were designed for tabletop. The situations that you're talking about are unique to Mu*s, and I generally think that you're smart enough to come up with some ideas that help transition from the tabletop to online. You don't, mind you, so you sound like you're shying at flies or making mountains out of molehills.
This is the preface to the following: WoD gives XP for showing up. You were there. You participated. How you take it from here is going to depend, but I prefer to think that showing up on a Mu* at all is worthy of a cursory thanks. If you want to use that cursory thanks to up skills you never use, then go for it. Call it a part of downtime.
RfK apparently folded the 'participation' part up into what kind of RP you were engaged in. Weighing one over another is smart. Hard to quantify and probably harder to qualify, but I like it. It's akin to a GM saying, 'Well this was a light day, so only 1 xp for everyone.' This is part of the table's rules and a right that's been given to the GM, sometimes explicitly. Without a GM, we need to find other solutions, and this one hits the right notes for what the RPG was going for.
This post has no grand conclusion. I've lost my train of thought, so I'm ending it there.
edit: @Misadventure asked me:
Did you miss that Arkandel was saying he didn't want to play up the practice/training side of being a boxer?
If this was the point, then I missed it like a skull-shaped meteorite misses the Earth, and Arc and I are in agreement.
What I thought was being said was, "I shouldn't have to play a boxer to raise boxing stats." I like my response to that—if you want to raise boxing then you better damn well have boxed somewhere along the line of the character's adventures—even if it's one-hundred percent inappropriate to what was actually said.