The post about is the best you can do with embedded VM. It will be a significant amount of work. I believe you will be forced to build transfers for users for literally every user.
e.g. ext range 100-119 (qty 20), with boss = 119
AA1 = digit 1 transfers to AA2 (on AA1 they are told to enter three digit extension
AA2 = digit zero transfers to AA3, digit 1 transfers to AA4
AA3 = digits 0 through 9 each transfers to the correct user (100 thru 109)
AA4 = digits 0 through 8 each transfers to the correct user (110 thru 118), with 9 (ext 119) routed to the desired assistant, or to another AA with a message and no options (effectively a disconnect)
so at least three (possibly 4) additional AA's for just 20 users, and a pile of work. Add one AA per each additional ten users. I don't believe the embedded VM AA direct dial by number can be used, forcing individual transfers. But I stand to be corrected.
Having the boss (plus any other extensions to be blocked) in a unique range would be by far the easiest way to do this using embedded.
GB