Looks like a nice boat. I reckon you could redo the beams, in wood composite, but this time make the beam so it can't rot. This means, no or reduced fasteners, all beams glassed, extra glass on abrasion surfaces.
I would steer away from alloy tube beams, of course it can be done but there are also cats with alloy beams which need to be replaced after a decade or two (or three). For us mortals, we have to use alloy tube we can find, which can be really hard. Then we often have to use over specced alloy beams instead of the correct engineered beam because the chance of you finding a tube of the exact correct dimensions is pretty much impossible - so you have to go heavier than needed. Then there is the problem of not being able to reinforce the ends without welding. Alloy beams have been used for decades but for fast and strong beams wood composite is used before alloy today. No racers I can think of use alloy anymore. Even alloy forebeams are rare nowadays on custom cruisers because composite ones are better integrated, easier to reinforce where needed and built for an exact fit. You can then integrate your mast hardware, tangs, tracks, walkways etc which you have to add on the alloy tube.
On top of this you then have to adjust your beam sockets to fit the alloy beam. So I would not do alloy.
How did the beams rot? - I know a Wharram owner said that a Wharram he knew of had issues with rot and I think the beam shelves and the notches in the beams could hold water but when done well there should be no entry point for the water into the timber. I would suggest remaking the beams of the same construction, maybe updated slightly with double bias glass and unis, but have the whole totally encapsulated in glass with only composite fittings - no bolts and fasteners ever will ensure you don't get rot again. But where they rotted is very interesting and very important to know how to fix the problem.
Then when you want to sell your boat is a better Wharram but not a Frankenstein with a questionable beam system.
