Just to repeat my solution. Group - ungroup button. When the party is ungrouped everything happens individually, when everyone are connected everything happens for everyone. Sneaking, jumping, movement. Whatever.
This was suggested since the beginning of the thread (I suggested it myself as a bare-minimum alternative to a completely redesigned control scheme, which would be preferable) but only as a partial workaround. Because it addresses only a general annoyance (having to group/ungroup characters individually) but not the core of the issue (1. being unable to select multiple units at once and to give them group commands).