MAX7414 low-pass filter OS pin
You can use any voltage reference since the OS pin will not load it (datasheet states \$10\mu A\$ leakage current). However, the voltage on the OS pin must be in range \$V_{COM}\pm0.1V\$. So, you cannot shift the output by \$1.65V\$. 

Keep in mind that the output offset settings is used as correction. The output is biased due to common-mode input voltage of the \$V_{IN}\$ and \$V_{COM}\$ inputs. The differential input amplifier used on the input has 70dB common-mode rejection ratio. This allows bias reaching only milivolts on the output. Bias by \$1.65V\$ would be far out of this range.