I don't recommend nuking, unless you plan to use the design field for new designs frequently, like a huge new layout for each event. Many people do this.
But if you plan to build a fairly permanent town like most players, i don't recommend it because you will not feel the town is complete until it's all restored, and that puts unnecessary stress on the project.
When I did my full redesign, it was upon the completion of purchasing all the available land (at that time). My method was as such:
I worked in sections, so I only completely cleared a small area at a time vs. clearing the whole board. This also keeps your inventory more manageable.
1. Start with one key area that you already have a vision for. Along the mountains, or the beachfront is usually where people have things they know they want there.
2. Clear out all the decorations in that zone and place buildings first, then roads. Then reposition the buildings to fit to the more restrictive pavement (because pavement only builds along preset grid lines)
3. Lay down pavement of a few main streets. Then line up a couple buildings which will begin your "down town" area. Almost all towns IRL are formed this way, so it will help establish a more realistic layout vs. having a town that looks like every single building surrounded by street. No town looks like this IRL.
4. Try to develop neighborhoods and districts similar to real life zoning laws. Residential, retail, industrial, rural, etc.
5. Leave empty space like they are vacant lots, for future building in each district, to avoid future redesign headaches.
6. Add a few key accessories to each building, then slowly fill in with greenery and other supportive features one you are certain you like the layout. It is tedious to recollect lots of trees and flowers if you realize the building next door needs to shift one square to the left for better alignment with pavement, and that will push the building next to it left as well.
Have fun, it's not a job is a game. Take breaks, and when you stop in mid progress, decorate with orange pylons and yellow traffic barriers so it looks like a construction site in progress.
When you are done, post pics in the Showcase section so we can all praise your vigilant efforts!
Happy tapping!