Isn't that exactly what we signed Son and Njie(admittedly, now injured) for though? We don't want to become overloaded with wide forward but not quite #9 type players.
Yes. And both NJ and Son could come on to fulfil that versatile role in time - they need to improve their finishing, playing the shoulder of the defender etc in short improve their CF play. Both have shown they have an eye for goal, but they are forwards who can stretch to playing as a CF. What we need is a CF first, who can play as one of the front 3 as well, because:
1) Kane is proving to be impressive at leading the line, his goal against Southampton an example of what he can do playing against the last man.
2) We have needed something different in attack in some games. Alli has provided impressive drive, but imo we need another player, probably an older player. Dimitri Payet who's 28 would be ideal. On the other hand we have seen Poch bring players on. So Dembele, Alli, Son, Lamela Njie could take a step forward to provide that fresh attacking dynamic that we miss in some games. But only Dembele is 28, the rest 22 or 19 in Alli's case.
3) If you are buying a CF, you want the best player you can get. If Kane is injured or suspended you need someone who can get goals. If that player has spent the season on the bench playing the odd cup game, they will not be match sharp or confident. But if that player just moves position - and indeed rotates position with Kane during games - then you are well covered. You are utilising your significant financial investment to greater effect.
I don't know about the other players who've been linked but Berahino might have been such a player who could rotate with Kane, during games or off the bench. Whoever it is, they should add something new to our forward play. We may not make a singing, but most agree, Son and Njie are not CFs. We need another CF.