I couldn't find a hard point with 4tpi aggressive tooth pitch so looking at Japanese alternative.
I am aware Japanese saws can't be hardened but as an occasional user I think I'll be fine.
Due to limited time to do woodworking, it's taken me ages to get to a stage where I can finally work on projects I've wanted to do for a while (building a bench took a few months!)
So spending more time trying to get a saw into working condition is a hugely unappealing idea, restoring hands planes was pita enough, and only did it because no cost effective quality alternative existed. Similarly for building a frame saw, it would be ideal but they only seem available as a kit.
I'll be sawing at angle and flipping the board so although the width is 250mm, I'll be sawing a subset of that amount in one stroke.
These are the largest pieces I'll be working on for the foreseeable future - they are left overs from an oak worktop I snagged from someone redoing their kitchen
You can sharpen disposable saw teeth, you just need to do it with a diamond feather style file and sharpen only part of the tooth. Eventually, you'll find the hard outer part of the tooth gone if you do it a few times, but you'll also probably damage the saw before then.
If you use a ryoba or kataba, you'll find that you have to bear on it in some woods, which may lead to problems.
I mistook your measurement when commenting earlier for reasons I can't imagine - 250mm being about 10 inches, I was thinking 4. It's going to be a tough slog. All I can recommend is that if you're going to have a go at it, cut the corners first with the teeth aligned to sever "up the straws" and not back into them, as in you're pulling the saw with the near corner facing you being long grain on the top and end grain facing you.
This is a job for a regular rip saw, and definitely not a hard point combo tooth - those would just rasp.