They're not really target men, more what they'd call a complete striker. Koevermans plays the target role in that when we played him at the top of a 433 he held the ball up well, but he's a poacher with good feet; Hassli is actually more dangerous outside of the six-yard box than in, when he has space to create something, and he's definitley not a target forward; his principle role isn't receiving and holding up the ball, and banging in headers from corners.
It could work. I think one problem is that the pairing of a fast forward with a big guy creates space for the big guy. We could play a wide diamond, I suppose, with a small, fast hole player behind them and the other midfielder as a straight-up anchor man in front of the backline; it's not very flexible but if you have the right players it can work.