In a line:
A top quality homely nursery with emphasis on the outdoors. (Ideally a chain of nurseries eventually).
Broken down:
Top Quality. I've experience of the low end of childcare. Places that make do with no equipment budget and poorly paid staff, often reliant on a lot of students. Life is a constant struggle. The middle quality nurseries are suffering from the government cap on the fees they can charge for the "free" places. If that goes up to 30 hours per week many nurseries are truly stuffed. I think there is room at the top. If you can make a nursery that is very clearly better by miles, I think enough people would pay a premium. And I think I know a few ways to keep costs down but quality high.
With staff you get what you pay for. A lot of managers are of the belief that great staff are incapable of recognising that £15,000 per year is greater than £14,000 per year. They're not. They want paying well, job security, and good conditions. I do believe that good staff save money in some ways. They use resources better, move on less frequently, are sick less, and generally make life so much easier all round as well as being better with children, parents and each other.
Homely. We would be competing with pre-prep schools for the over 3 year olds. They are very school orientated of course, but a lot of people are quite against schoolified environments for such little children. The nursery would provide the homely atmosphere many people are really keen on. Smaller numbers per room, a homely look, a learning through play style.
Outdoors. Not a month goes by on Mumsnet without somebody saying they'd like to set up an outdoor nursery. Backpacks on and off to the woods. There are a few round the country. I'm an outdoor type person. I walk, cycle, and camp, but I really don't like the idea of being fully outdoors. On a wet and windy day with driving rain...no thanks. I know children love to be outside, but feel they need the security of a warm and snug building as well.
The nursery would have an impressively large garden with all the usual toys and equipment, but more wood and less plastic. There would be a lot of natural "loose" material: planks, logs, branches, etc. The nursery would also have land. Woodland ideally, or a large grassy field would be good too. It wouldn't be garden and agricultural/woodland is fairly cheap. Access to a common or public wood would be great as well. The right location is kind of essential. Near people with some money would be handy.
There would also be a 'barn'. A cheapish agricultural type roof on posts would do. A few lights and you can be sort of outside every day of the year no matter what the weather is.
The building. Another big saving here. If you're setting up a top notch nursery in a town you're going to need a fancy expensive building. As this nursery will be a natural outdoorsy nursery you can have a much more 'rustic' cabin type affair. I've even seem some rather fancy tents that would have been fairly good if it wasn't for the fact there were very few windows. It's almost certainly going to have to be a new build because of the reasons below.