@Italiangreyhound
In the past there were areas where people did this- rented near the school temporarily, got the place, then never moved. A lot of councils decided this was unfair, and now require proof that you are actually living at the address (e.g. council tax payments) or simply will not accept this as your address if you have another house nearby (say in the same town). In this case, they usually run your application from the address they consider your home i.e. your old house. In this case, some people may still get in, but others won't, and will have a nasty shock on offers day.
Also, some parents will report this behaviour to the LA- especially if their child missed out on a place. This would be investigated by the LA, and if they believed you had behaved wrongly you would lose your place- even if the child is already at the school. This is obviously difficult for the parents and the child.
So it's not a good or safe course of action. Some people do get away with it but more get caught these days I think.
I agree all children should go to a good school. If all children were forced to go to their local school, it might actually cause a raising or evening of standards.
The reason people view this as morally wrong is that by behaving this way, you are depriving another child of a place. This child may actually live much closer to the school than your child, and may be left with a long and difficult journey to the next nearest school with places. If 20 or 30 people did as the OP is planning, then that's 20 or 30 children who will have this problem. In some areas, where all schools are very oversubscribed, this can lead to "black holes", where children are left without a school place at all.
Some schools wish to serve their local community, hence setting distance or catchment criteria. Those renting from outside of catchment may disrupt a school aiming for a community feel.
I live in a county that is largely very rural. Each school has a priority admissions area defined by the council- organised for the provision of buses etc. Not every child is in their closest school's priority admissions area - it is designed mostly so that those with a 5-7 mile journey to their nearest school get that (with an organised bus and friends to travel with), rather than, say a 12 mile journey with no provision.
I know OP has said she intends to move to that area, eventually. But basically everyone who tries to do this says that, and many of them do not end up moving as they can't find a nice house or live in a nice enough area.
If people could rent another property to create a loophole in the system, it is often poorer children who lose out.
So that's why people (and schools and councils) don't agree with it.