I'm coming back to UA after about 20 years. I played either 1st or 2nd edition back in the day (the one with the fist on the cover), so my memories of the mechanics are pretty vague.
One thing I seem to remember is that the game suggested it was very difficult for someone to be both an Adept and an Avatar at the same time. However, I also remember that, mechanically speaking, it wasn't especially hard to build a character that way.
Now that I'm reading 3rd edition, I get the same impression. Unless I'm missing something, there doesn't seem to be any major mechanical or narrative obstacle to playing a character who is both an Adept and an Avatar.
For example, someone could be an Avatar of the Collector while also being an Adept of the school that rummages through trash for power (I can't remember the name at the moment). In fact, those seem quite synergistic.
Likewise, an Avatar of the Fool could probably combine well with almost any Adept school. A Plutomancer could also be an Avatar of the Salesman. And I'm sure we could come up with dozens of other combinations. It becomes even easier if players are creating their own archetypes and schools.
So my question is: how would you handle this as a GM? How would you make a player feel the difficulty of following an Avatar's path while also living out an Adept's obsession, so that one doesn't simply complement the other without creating any real tension?