If your main goal is to improve ignition of small charge weights by increasing the loading density, you're going at it the wrong way IMO. You'd be better off to use a bullet with a short nose and a long body to better fill the case - something like the old Lyman
Loverin designs. Lyman's 350457 (250 grains) in the correct diameter would be perfect for your use, keeping most of the long bullet within the case.
Trying to design a bullet which will meet your goal
and still be useful in bottlenecked cases will result in very compromised performance in either or both. A custom mold builder (LBT, etc) should be able to make a on-off mold for you and not require a minimum order.