I don't understand how sideboards can somehow be half implemented but we've basically gone through this so many times so whatever seems best.
The first thing that came to mind when Kryder mentioned this was the we would get SB for the top 8 but that's it.
It would still allow for the dynamic of trying to correctly predict the meta, since you would be locked into the deck you built without any sort of SBing for the majority of the tournament and likely won't make it into the top 8 in the first place if you can't build a deck that can correctly combat the meta.
Having SBs in the matches of the top 8 would potentially make those games more interesting (and these matches are already the big draws for spectators), and also help to prevent situations where you don't end up getting bumped down slots in the top 8 because you got a bad pairing.
The example above I used was playing a deck that doesn't run any enchantment removal at all. Imagine that you decide to make a meta call and not run any enchantment removal in your deck at all. Your gamble pays off and only one other person in the entire tournament runs a deck where enchantment removal is highly relevant (Tutelage for example). Depending on the number of people in the tournament and how seeding is done you may never even come up against that one bad matchup, and even if you do if you are doing well enough you could potentially afford to concede those matches to them and still potentially make it into the top 8.
Once you make it into the top 8 though, what happens if that Tutelage deck also gets there and you end up getting paired against them. Suddenly you are playing your most important matches against the one deck that wrecks you that you specifically (and successfully) built your deck to avoid in the first place, you can't even afford to take the loss here and move on either, since these are the matches to determine the top 8.
If SB were included for the top 8 in the above scenario at least you would have the option to SB against them for those matches, so bad luck with matchups may be less of a factor. Things would be fair in this case also, since the Tutelage deck would also be able to SB in these matches, so they aren't getting punished for making smart meta calls either any more than the example deck.
I feel like it would be a decent compromise between the "we need SBs" and the "SBs are the devil" factions that seem to have developed around here.