I basically agree with what @SamWilby said here. A few possible additional things to note:
A level cap doesn’t actually exist in the game. A suggested stopping point of level 10 is written in for 2 reasons:
- Higher level characters are usually powerful enough that engineering challenges for them can become difficult
- The core rules don’t include attempt balancing or information for encounter challenges past level 10
- This includes balancing in terms of the increased number of feat points you would have
If you want “insane levels of abilities” you should do this via feats rather than higher attribute scores, or more commonly through the items they can get or achieve making for themselves.
You can easily make a “super long and difficult” campaign with the current idea of stopping at level 10, or going beyond to level 20, etc. Remember that levels are different for OL than compared to say D&D. Level 5 is really like level 12 (12 XP), level 10 is like level 27, as you gain increases at each XP. So level 20 would be like level 57.
You would have to define the “attributes for feats” thing far more in depth. Personally I don’t like it b/c Feat points are more valuable than attribute points. With what you wrote, for example, I could spend 3 Attribute points to get something to a Score of 2, then bring it down to a score of 0 and get a feat point. I could do this several times, getting a 3:1 trade going.
Feat points can be very powerful, in fact, I was considering making an encounter guide that instead of using levels to balance an encounter, it bases it more on feat points (or number of 3 point, 2 point, and 1 point feats to be specific). That’s how much feats matter in the game.
I think you’ll be surprised at how powerful characters already are at the higher levels. Especially starting at Level 5, and certainly at level 7+
If you are wanting to make sure you have a longer game, than it is about slowing down progression rather than giving more levels, and remember, OL already says you can go past level 10, you just keeping using the system as is, in that you still have the same attribute caps and point progression for XP.
Now, 2 things you could do for a longer game:
- Allow the attribute cap to increase from 9 to 10 at some point, like level 15 or 20
- Make another variable, let’s say EXP, that you give out. It takes, let’s say, 5 EXP to get 1 XP
- Naturally you can just do this by giving out XP more rarely, and awarding Legend Points instead (and you could increase the cap of 10 max legend points you are allowed to hold onto as well)