Just some random thoughts:
I really like Barkov... but other than position, there is no way he is better/more valuable than Drouin.
If there is even a sniff of Drouin dropping to 4th, and Nashville willing to trade the Sabres should be all over it (assuming its not an insane asking price). Grigorenko + 8th would be a no brainer for me (and I have high hopes for Grig) but I'm unsure this would get the job done.
More realistically, after DR's 'centres' comment...... I'm starting to believe Nich may just fall. Maybe not to 8, but the 6-7 range. Again, I'd love to see Sabres make a move and get him.... I think the forums would explode either way with this one as he seems to divide opinion pretty strongly. I personally like him and his potential is just too much to pass up (particularly since we have another first).
If for some reason Nich falls to 8 and they take one of RR/Nurse over him, DR should be sacked IMO.
If its 8 and the top 7 go as expected, then I'd target Horvat - nobody else. Maybe try and move down a spot or two if they can. I mentioned in the draft thread - what are the chances of moving both 8/16 for two picks in the 10-12 range, grabbing Horvat and one of RR/Nurse/Zadarov ?
Edit - I don't want Ehrhoff to be moved. As of right now he is clearly the Sabres best D IMO... and it would send a bad message, signing for a long contract and then trading him a year or two in.