Looking at booking SYD-KUL-DAD & taking a pun on MHupgrade on the SYD-KUL-SYD sectors. All the Economy fares on the website book into O class (even the fully flexible one), which are not only non-earning with partner programs (would rather not have orphaned miles in Enrich with their hard expiry), it seems from other people's experiences here the much higher cost to upgrade wouldn't really be worth it on their lowest fare bucket.

I'm assuming there's no way to book into a higher fare bucket through any self-service channels without calling MH?

Also, I was wondering what the 'sweet spot' is in terms of which Economy fare bucket to book into when considering the potential bid pricing for upgrades?