I dont think that you would have to learn scaleform and c++... I'm not sure but I think, its completely done with the weapon xml. pick the SCAR.xml as an example, there is a possibility included for adding a silencer. depending on the attachment, you should try to add a part very similar to that one which is intended to attach the silencer properly (you find that at the bottom of the xml). Of course you'll have to change it a bit for the acogs (i think you need things like "scope mode" , for more examples look in the rocketlauncher.xml and maybe some original crysis xmls but dont copy them
)to execute the attaching process during game, you should use a flowgraph, there are nodes provided for this. I already tried that whith the silencer, if you are interested, I can load up my fg.
of course you also need to setup an attachment xml, therefor, you can also take the silencer.xml as an example.
by the way...would you mind loading up some examples, if your custom attachments work?
like ceylonfarmer said, i do not think that things like that are here on the forums yet.... and the community would be very happy