Finally, views do differ, i'm sure others have opinions that do not match mine.
I don't see anything wrong in what you said. I'll add some detail
on what we're doing in case it's helpful (or if someone can
educate me if I'm doing something bad):
I use MTU 9000 on my transit connections, coordinated with the transit provider, because there seems to be no harm in doing that.
I use MTU 9000* on all my router-to-router links because I need
to be able to carry larger-than-1500-byte circuit traffic. If
nothing else, circuit VLANs all need to be a bit over 1500 bytes
on the outside (i.e. with my tags and possibly tags of other
carriers involved) so that they are 1500 bytes on the inside. *
Maybe I should/will-need-to change this to 9000 + a bit to allow
for 9000 inside.
I'm 1500 bytes at the customer edge for Internet. I'm also 1500
bytes at IXes.
-- Richard