To really make use of the extra transistor stage, one might want an extra capacitor in direct feedback at the OP. Than some capacitance at the output can help to keep RF away from the OPs.
The OPA209 is not really happy and low noise with 10 K resistors. At only some 1.8 V, one can use lower resistance values (e.g. 300-1000 Ohms). A 10 K resistor also has significant noise, way more than the OPA209.
Pots can be tricky with drift and a not so perfect wiper resistance. The reference is not really good at low frequencies (e.g. 10 Hz), the high frequencies are set by the filter and not so much the reference. So there may be better references instead of just a super low noise regulator.
Depending on weather the ground connection matters, one could have a reference for the sum and than an extra buffered center. This may especially help with the low voltage. A similar circuit could have the negative side of the reference at the negative side.