I also started thinking about applying Angry’s XP advice to Open Legend when I read that article. But first off, I haven’t run Open Legend at all yet, so I’m wary of modifying the rules without personal experience first.
That said, here’s some thoughts on how to do so. As others have said, each XP in OL is like a level in other RPGs, so I’d design the system to keep that in place. If we’re aiming to gain 1xp per session or 3xp per major milestone, you can tune the reward system to get close to that. The GM determines when to award XP, so all we’re really building is the GM’s rules for when to do that.
Angry’s advice is based around encounter difficulty, and we already have that in OL, we just have to extend it out to non-combat encounters. We don’t need a hard rule for this, just decent judgement. So we say we’ll award XP after the players earn some number of progress points, and they get specific numbers of points for completing meaningful encounters of each difficulty, plus they get points for completing milestones, plus you can award points for whatever actions you want to encourage such as exploration/discovery.
That last part is 100% my motivating interest in this system. And it’s also why, even though this is a rule the GM imposes on themself, it’s vital that the GM make these rules clear and open to the players. Because rewarding behavior you want to encourage only works if the players know about it.
So in my mind, we’re not changing the rules of OL, we’re just making up guidelines which GMs can use to design the reward structure of their games.