Unfortunately, none. Furthermore, with the exception of MX7600, Canon seems to have abandoned the field of heavy duty inkjet AIO's.
And while the MX7600's opaque cartridges are very easily refilled as shown by jtoolman's videos, there is no refilling option for the reactor "PGI-9 Clear" liquid.
For the rest of the printers, even if you skip the opacity problem (which isn't difficult to deal with the Durchstich method) the cartridges too small for serious usage. For example it's impossible to print a large duplex document without having to replace some carts. That means the user has to be close to the printer which is a waste of time.
I am faced with the same question as well. Once I make sure that there is a reliable option for refilling (or refillable cartridges) and resetting, I am going to suggest to my friends an Epson BX635FWD or a similar model instead. Their capabilities match Canon's old line of serious inkjet AIO's (MP750, MX850), dealing with 4 cartridges instead of 5 is easier and pigment inks are a better option to dyes (at least for my needs).