Robert, welcome to the site and good question. I think anytime you alter anything from stock you are going to diminish the value of it from a collectibility perspective. I think it boils down to what your plans are for the bike. If you are hoping to sell it later and want to get the most you can for it, you're probably better off leaving it stock instead of doing the mods you mentioned. On the other hand, if you intend to keep it and are looking for more performance out of the bike than what you have, by all means, do the mods and have fun with the bike! If you plan on putting quite a few miles (say, 30,000+) on the bike and you just want a nice reliable ride without really affecting re-sale value one way or the other, then just do the gear-drive cams.
I have built my SEEG the way I want it with both engine and accessory mods without any concern for re-sale value . . . . . . because I will never sell it. On the other hand, I don't plan on doing much of anything at all to my recently acquired SERG at this point (regardless of what 'd00d & S/B think

), because I am actually quite pleased with it in stock condition. Also, the bike has just 15,000 miles on it and it will be lucky to see another 2-3,000 a year, so the tensioners shouldn't be an issue for some time to come. In other words, I have done and will do what makes sense to me for both bikes with the way I intend to use them in mind.