Well, I'd wager it would be someone who can if necessary play like Kane does to an extent, but otherwise possesses facets to their game that allows for them to be played on different positions to maximise rotation.
Bojan's a great little player, but, having looked him up, he's actually even shorter than I imagined (quick search puts him at a shade over 5'6): he may be able to play as a false nine/wing forward and completely differently to Kane, allowing for rotation, but there's no way we'd be able to play the same way we currently do if Kane's out and Bojan is our other option.Balls up top wouldn't stick, we'd rely much more on ground passes and balls into space (as opposed to letting Kane bring it down and look for options from the long pass)....it would necessitate a big change in the way we play, which sort of defeats the purpose of bringing in cover for Kane, really.
I think that is why we were interested in Berahino in the Summer (and I'd be surprised if we're not still interested in him). He is primarily a number 9, but can also play 7, 10 and 11. While Berahino isn't as powerful as Kane is, like Kane he does like to drop deep to receive the ball, peels out to the channels, finds goalscoring positions in the box, is a decent dribbler and is able to get quick shots away with both feet like Kane is. What we would lose in terms of physical power we would gain in terms of a bit of added pace.
I think signing Berahino would give us the following options:
Note that I have used number 4 as holding midfield position and 8 as box to box.
Player ____ Primary Position___ Other Positions
Kane _____ 9 __________________ 10
Lamela ___ 7 __________________ 10, 11.
Eriksen ___ 10 ________________ 11, 7
Alli _______ 10 _________________ 8
Son ______ 10 _________________ 7, 9, 11
N'Jie _____ 11 __________________ 7, 9
Chadli ___ 11 __________________10, 7
Dembele _ 8 _________________ 10, 4
Mason ___ 8 __________________ 10
Bentaleb _ 4 __________________ 8
Dier ______ 4 __________________ 6, 2
Carrol ____ 8 _________________ 10
Berahino _ 9 _________________ 10, 7, 11
I have left Onomah and Pritchard out of this as I don't think that we have quite seen enough of them in the first team yet to judge the positions they can cover. I have also left off Townsend as it seems he isn't part of Pochettino's plans at all.