Fitting A Filling Loop To A Back boiler System?

I have a conventional backboiler system - boiler and pump downstairs, cylinder upstairs.
Whenever I drain down to do any work, then refill using the F & E tank I always get air locks that are a nightmare to purge.
If I fitted a filling loop to the system, and refilled with mains pressure, would this make air locks less likely?
Where would be the best place to put the loop? I can access the boiler and pump pipework from the void under the downstairs floor, where there is also cold water pipes running. There is also a mains cold water supply near the cylinder upstairs.

Thanks for any advice.

Are you simply talking about fitting a loop purely as a means of backfilling the system or converting it to a sealed system?

Just to backfill.

Although it would make it far easier to fill technically it is not allowed due to the remote possibility of 2 faults occuring .
1. filling loop doesn`t turn off properly or gets turned on accidentlly on if left connected
2. Although remote you get a blockage that would result in the open vent/cold feed being closed off.

Result boiler then becomes a pressurised system without the relevant safety devices to stop the big bang