Thing that worries me is when I lived at home with parents & we had moved, we kept Marley in for the 2 weeks. Me being the worrier I am I thought as soon as we let him out he would do a runner, so we got him a harness. He was fine in the house but as soon as we got comfortable walking around the garden, the neighbour came out & called her husband to come see 'the cat on the harness' & Marley got freaked & got out of it in a split second. He then ran off at 100mph! He did come back thank god but with Leo, he has never even had access to the outside world. He doesn't know all the potential dangers that lurk so wouldn't last 5 Min's if he came across a road. If Marley got out of the harness I'm 100% sure Leo would be able too & quicker.
Also as you mentioned, Id hate for him to be pining to go out when he couldnt all the time. He can't miss what he has never had..My dad does make me feel bad though as he doesnt think its normal for a cat to be indoors 24/7. (sorry sliding off subject)
Ive figured that until I move into a house I will wait until I introduce Leo to the outside world.