Didn't want to get into a deeper discussion during the game not to influence the voters with my opinion, but here goes:
I think the position you are describing is more of what Kun did when they both played together rather than Forlan. Forlan was the central forward and dropped deep, but it was Kun with the more free role:
Example of the game vs Fulham in EL.
^^ vs Valencia
vs Villareal
For me during his best time in AM he was the central forward and the main man.
The role you are describing is more of his Uruguay role where he played off Suarez.
There you have a point, but here we're talking about the league and to be honest I can see Suarez and and Kun a lot closer to the style that would make a much better match when you use Forlan in a combination of front 2.
Now for Crespo I can see him doing well in 4-3-3 as a lone up top and/or in 4-4-2 but in the same position Forlan occupied in Atletico. At Lazio he played in close to the same role as Forlan at AM and Claudio Lopez was on the leftish role feeding off him. In Milan he played with Sheva, but then Sheva is a bit different because his versatility helped him play with pretty much anybody apart from Crespo.
For me Crespo was best in his Lazio years, really deadly and possibly in his best shape in his career. Put Aguero next to him and I'd like that, Forlan... not so much. I think a lot of their roles and qualities will overlap and you can't get the best out of them in that formation.