Yes, now that there are more frequencies available, why don’t D@D get themselves a practice freq?
In principle possible, but the cost to replicate all of the existing tranceivers on 121.500 around the country, and the landlines from them to Swanwick, plus the fact that many of the recievers have DF capabilities etc. etc. means that it won't happen. Unless you are envisaging a practice frequency that could not handle a training fix.