Well, my state inspection sticker is about to expire so I had to get my hi-beams working or buy a new combination switch. Thanks to this forum and
this DIY article, the combinations switch is fairly easy to access on a W210 chassis. I was successful in removing the steering wheel without a helper (check out the first attachment image). The 3' breaker bar was practically a necessity as that bolt is really torqued down + blue Loctite.
After a little bit of examination, it appears that the hi-beam contacts are accessible (see last 2 attachment images). The resistance between the non-momentary contacts was measuring over 500 Ohms which is too high I guess. After a bit of cleaning/scraping with a small gauge wire and slightly bending the lower copper tab towards the mating contact, the resistance is now less than 10 Ohms which is enough for my multimeter to chirp when put in diode tester mode.
Reassembly was a breeze and it lo-and-behold, non-momentary hi-beams are back! Aside from the hi-beams, the rest of the switch contacts are pretty well concealed inside, so issues with any other functions would probably mean a new combination switch.