What is the problem?
Holding a note on the grid ignores aftertouch.
If, for example, I have the filter cutoff controlled with the aftertouch, when I press shift to hold the note it ignores the effect the aftertouch had on the cutoff value.
What should this feature achieve?
It should maintain the aftertouch alterations to the held note.
In the filter cutoff example, any changes made with the encoder would use the held note filter cutoff value as the base.
Are there any workarounds?
No
Any links to related discussions?
No
Any references to other products?
No
I’m not really sure if this is something that would be useful to everyone but I find myself discovering a sweet spot and wanting to hold it but when I hold the notes it changes to the “un-aftertouched” state. 
Maybe it could be a global or per synth option in the menu. “Aftertouch Hold”.