Considering netting my full allotment

The simple answer is - it depends how big the holes are!

There is a plot on our site that has done just that - it must have been a long while ago as it is now full of large holes!
Remember though that if you do that you will be greatly altering the natural way of  things, for example you may stop birds coming in, but as well as eating some of your crops many birds also eat lots of pests. Their droppings and feathers and even dead bodies add to the fertility of the soil

Could be a permanent home for some. 

  I agree with all the above.  I use netting on my brassicas only and build a temporary cage with it - quite large holes but small enough to discourage the cabbage whites from getting in.

If you're new to the growing game have a chat with fellow allotmenteers about the pests which are common in your area (for example, allium leaf miner and leek moth are unlikely to be a problem where you are - yet!)

Then use netting with the appropriate mesh size for the job - any other approach would be completely OTT and possibly also inappropriate for where you are and what you intend to grow.