Selling, buying, or trading extra copies is an explicit violation of the Steam Subscriber Agreement. If Valve finds this happening, they can and will permanently disable the accounts of all parties involved (the seller
and the buyer).
From the
Steam Support article on extra copies:
May I Buy, Sell or Trade my extra copies?
No. This violates the Steam Subscriber Agreement and may result in all involved Steam accounts becoming permanently disabled.
The only thing you are legally allowed to do with extra copies is simply give them away.
Furthermore, OP, what you're talking about wouldn't even work anyway, because you aren't going to have any giftable extra copies of any of those games, if/when you do buy that pack. As a nearly universal rule, when you buy a pack containing games you already own, you
do not receive extra giftable copies of those duplicate games. You do technically own two licenses of the game, in these cases, but Steam licenses are non-transferable, so you just have to be content with technically owning a license of the game that you have to keep. The
only exceptions to this rule are listed
here.