Hmm, I let the decisions about Yangon merging totally up to you, if you see some natural river that clearly limits the boundaries better shape the already existing boundary to follow the river, e.g.
BTW, I read in the wiki to avoid connecting the boundaries directly with rivers or other physical ways, not sure if you agree about it:
osm.wiki/Relation:boundary

Yes please, I agree with you. Do the mergings as you consider. Meanwhile I'm merging the outter districts/regions to the current Myanmar level=2 boundary (the country borders will be respected carefully).

Ok, thank you. I checked the country for administrative boundaries ways and relations a couple of days ago and there was nothing yet, you uploaded it recently? Do you have a link of the changeset?