Your chair does not appear as beech to me (maybe lauan or related?). You're right, though, that oil will darken the wood and splashing water on the freshly-sanded surfaces will provide a good idea of what oil will look like. 2-part wood bleaches are powerful oxidizers and working with them requires every safety precaution. I'd avoid them altogether and consider another course such as a toned or pickled finish. If blonde wood is what you're after, best to start with  lighter-colored furniture woods like beech, maple or birch.

Considering what you have there (see your other thread), maybe you shouldn‘t mess around with it too much. 

@Herringbone Thank you very much for your reply. They look pretty much alike indeed, my chair has much more screws though (perhaps it is a copy, or a previous owner added more for stability?). I agree, bleaching is risky. I've also seen a black lacquered version of it but I'm not sure I like it. I really want my chair to look more like the one you posted on the other thread.

Do you have photos where more screws are visible? Would be interesting. 

@Herringbone The red arrows point the extra screws and the green arrow shows the screws that are accurate to the Illum Wikkelsø armchair. All the "extra screws" are a little smaller that the accurate ones at the front.

I can hardly imagine this being a knock off. The design seems to be pretty rare, meaning it wasn‘t much of a success. Plus: The construction is rather uncommon. The screws could have been added Or omitted some time in the production period. Or some owner put them in to enforce the construction. Did you disassemble the chair? Do the  screwholes look like they were done for a reason and by professionals? 

I'm not sure if this is the route you want to go, but I find that india ink dyed wood with danish cord is really beautiful. It is also extremely easy to work with, and would only need some paste wax as an additional finish.

Maybe because this is a rare chair you don't want to go that route, which is understandable, but it would look really nice.

@herringbone I have not disassembled it and I'm not sure I will as it is very sturdy. I had a similar problem with added screws by a previous owner with two of my Niels Møller 78 chairs, I removed the screws as the chair had to be re-glued and they left two big holes that were a bugger to fill and color match with teak. I understand by now that bleaching could really mess the chair. @frankielemmons I thought about India ink dye too (I also found online an Illum Wikkelsø chair that has been refinished with black lacquer) but I don't think it would look good in my living room.

I think I'll complete the sanding and proceed with danish oil and wax. Is there any other way, complementary to sanding, to revive sun bleached wood and bring out the wood grain and its natural color?

You could try treating with oxalic acid which should be available in dry form from better paint or hardware stores and is cheap. It is not a bleach per se, but it can be effective for removing or lightening mineral and/or gray stains caused by exposure to weather. Again, all safety precautions should be followed, especially when mixing dry crystals with warm water. Avoid breathing any dust! Otherwise, follow directions and two or three treatments may produce better results. Worth a try, IMO.