I don't think the notion of consolidating picks and trading up is specific to any one player. In terms of bigs in general, Wiseman is in a league of his own and I don't think there is any chance we get a shot at him and I am not sure Okongwu is worth trading up for.
It is not that Okongwu isn't a decent prospect, but the problem is that you don't know really if he is going to be any better than say Toppin, Achiuwa, Jalen Smith or Isaiah Stewart. This is the NBA draft and you really never know, so why trade up for these guys. Especially bigs are very low on their development curves so it is really impossible to project their NBA performance relative to each other unless you have someone like Embiid (and even then, there have been major busts).
Skill players are a little more developed often but there is still difficulty, again, except for the really top tier players and this draft may not have many if any of those.
Bottom line, we really don't need the 26th or the 30th pick so trading one or both to me is not a big deal either way. Unless I was really sure about a player, I don't think I would trade all 3 for just one.