Well, I always have a couple of tall centrebacks, so I just make sure that my tall centre back is playing in the position which is told to go up for the near post flick.
If I were to change it because of a missing player, then I'd probably just swap the near post flick instruction with another player who had high jumping and strength attributes. But on the whole I keep it the same. Means I have far less fiddling to do.
As an example, at Arsenal I used to have Senderos and Richards. Senderos would usually start, and Richards would replace him if Senderos wasn't available. At Barca at the moment I've got Vidic and Corluka.
Worked a treat in the lower leagues too, where I had one guy with jumping 17 in the Conference regional and another with 15 who I would rotate.
But, if you don't have that sort of squad, just make sure that your best player (and only your best player) is set to the near post flick and you should bag yourself an extra 10 goals a season (providing they're any good).