My personal opinion is this is getting overly complicated. The inspection port and repair needed for the rudder you have is inexpensive and simple. Making that fix doesn’t preclude you from making the upgrade to a new style rudder later if you decide it is necessary or desirable. And you could over time keep an eye on eBay and this board for inexpensive used pieces for the upgrade. So I’d fix the boat as it is, sail itband decide on the upgrade later.