We cut a lot of 45 degree miters so rather than changing the saw blade angle it makes much more sense to make a carrier for your wood. Use stable plywood and 2x4's for backing up the basic plywood base. Make everything you fasten adjustable so you can fine tune it occasionally. I guarantee you will be adjusting it - maybe only once a year but you will. That's the only problem with using wood. Of course you need the saw blade to be exactly 90 degrees and the best way to get that is to buy one of the digital angle finders - one of the best inventions in years. I have an original Wixey Digital Angle Gauge but there are many out there now. Another great invention is the Bessey Auto-Adjust Toggle Clamp in the photo below. One semi-permanent one at the backed up edge and an adjustable one (using an inlaid T-Track) at the leading edge. Where the blade exits the wood I have attached a block of Wenge or other dense hardwood to help prevent splintering. Eventually it wears out and needs to be replaced.

This jig is sized for our boxes. I can see a use for one that is much larger. The clear piece of plexiglas is an adjustable stop. I cut all the pieces for a box to the correct length and then cut the miter - the stop is adjusted so the cut leaves a razor edge and the length stays the same. A standard crosscut blade with small stiffener plates is used.

Of course the entire jig is fastened to a track that slides in my tablesaw miter gauge slot.