Battery powered 4-20mA sensing application
In answer to your question, the ungrounded supply will not contribute to ground issues, but there might be other connections to your system.

If you draw 20mA at 14V it will Likely draw close to 100mA from the 3.3V supply. Other than that it looks fine, assuming it’s a 2-wire P to I transmitter. 

Shielding depends a lot on the exact setup and where, if anywhere, the circuit has an earth connection.