About the AI: Way too much work for so little added value. The AI as it is now is "fine" as it is now, in the sense that as long as you don't play cards that it doesn't know how to use, it will win most matches where it doesn't brick (and in those cases you'd probably lose anyways). There are some cards that could use a fix, but no way they're hardcoding the correct behavior for thousands of cards and interactions. (Also what's with the SD cheating? Never heard/seen this)
About "PvE content": I somewhat agree on this. Even with autoduel farming SD is just a chore at this point, no point trying to win against vagabond when you only get 250 extra xp over losing, and the constant wait-10-turns-then-deal-10k-damage LD farming gets old at times.
What I'd like:
Replace the shitty weekly quests with bingo (with much smaller rewards of course, like even 50 gems per week plus some gold would be better than what we have now).
"Super LD" that are actually hard to beat instead of hard to farm. Give them op cards, give them op skills, give them special vagabond-style rules, give them double LP, give them a second draw per draw phase... Just a boss that's legitimately hard to beat, then make the rewards based on wins instead of DA.
But once again, this would be a lot of work for (relatively) little added value, so it probably won't happen.