What you show is only the first stage of a classical op
amp (delivering well less than full output swing and nil
output drive).
The second stage must track and match the first for
any decent Vio performance (else systematic errors).
So you want a rack of matched current sources.
Now you mention "reference" but really the one shown,
and the others I mention, are "repeaters" from a not-
shown reference.
While bandgap-style is most popular (leading to low
voltage and temperature sensitivity) I have seen low
power "programmable" op amps with an external
set-resistor biasing the current mirror rack. If you
are on the hook for the signal chain and nobody
cares how you set the biasing, this could be a simple
work-avoidance, schedule-friendly play.