@Scott Savard I have purchased two lots and built houses on them. I am also an Architect that has done this numerous times for my clients. I tell you this because I think you have too many contingencies. The list you have may take a year or more for it to be approved and I don’t think a seller will go for that.
The septic, survey, and easements requirements make sense. Those are easy to do. The other items are complicated. This is the order that it will happen.
1. First you will have to subdivide the lot which takes time. Does this require a variance? You can verify with a simple phone call to the zoning or planning department. If it needs a variance you are in for an uphill battle.
2. The design review committee has to approve the plans. Are you sure this is a requirement? Is it the city review board or some HOA review board?
3. Building permit. This is easy and is not a concern.
I think you can ask for a few extra months if you need a variance to subdivide the lot. After that getting a home approved by a committee and a building permit is no problem. Unless you want to build an enormous house that is not in character with the neighborhood. I would do more homework, for example, how much are utility connections going to cost? This can be a very big number.
Another option is called, “the right of first refusal.” Let’s say you offer $100k which is $50k lower than the asking price. The seller doesn’t like the idea but you tell them they can keep it on the market. If someone else offers a better chance you can match it or forget about the property and let the new bidder buy the lot. They seller may be more keen to give more contingencies. Of course the downside is you don’t have something locked in.
Good luck.