How viable is it to play a vassal of Asturia in 867 for a new player?

I'm asking not for me (I got 2.2k hours in CK3), but for a friend I've recently introduced to CK3. We made only two games so far. One feudal in the HRE in 1066 (seemed like a good tutorial region, and he thrived well until the save corrupted), and one current game in China starting 1066 (the guy single handlely avoided a division tension by being Minister of Work for two decades).

Anyway, I want to make him try different experiences, and with the next DLC focusing on christianity and Europe, I though that the Iberian Struggle could be a nice opportunity for him to try a different experience while still playing with the DLC new features and being feundal.

However, I was curious if Iberia was even substainable. I can't recall seeing it survive much whenever I play in 867, and the two times I played in the region, I helped crush it. So I actually have no clue if Asturia is viable or not, especially as a vassal of the king, and not the king himself.