Maybe he should have AMF as a secondary position for the following reasons:
First of all, this site (
http://www.spox.com/de/sport/fussball/0 ... eil-4.html) claims that to avoid large gaps in midfield using Rappan's verrou system the whole team usually had to play very deep in the field, thus Abegglen must also have been able to play as a more "defensive" variation of an inside forward. In PES terminology that would be an AMF.
The second reason why I would assign him AMF as a secondary position is a limitation of the game engine itself that at least PES 6 is subject to: you cannot play with just one midfielder. But if one wants to replicate the verrou formation in PES one would have to use a sweeper behind a centre-back and two full-backs, one defensive midfielder just in front of the back line and five strikers, two inside forwards, two wingers and one centre-forward. But due to the limitation of the game engine this formation is impossible to replicate unless one modifies it. One solution would be the one MagicDip has used in his own version of this formation (btw, thank you for all your formations

) which means that the two full-backs are used as defensive midfielders to achieve the minimum number of midfielders. The other solution would be the one I favor: to use the two inside forwards as attacking midfielders.
Same goes for the other swiss inside forward Eugène Walaschek.