"Position and Hold" has long been a sweet sound for me...especially after grinding through a line of departures ahead.
Problem with P&H is that it puts the PIC in a situation where he/she has no clear authority to proceed withut further instruction. In the air, this is not a disabling issue, on the ground it is much more ambiguous. In the P&H position, any trouble that is coming is likely going to be invisible to the PIC; the only indirect information available is from radio trafic and 'gut feel', and authority to deviate from P&H is not well defined, even when intuition says something has gone badly wrong.
From the P&H position, the PIC has a short list of options: a) Take off - hardly likely without a clearance, b) Clear the runway - also unlikely without some external advisory...and often difficult for larger aircraft because the 'on-runway' hold position is typically ahead of a convenient taxi-back position, so a slow and careful and possibly impossible turn is required to 'undo' the on-runway hold, or the alternative is a taxi down the runway to the next intersection. These things are also not normally achievable without tower communication. Or C) stay there and suffer.
SO - the worst problem is - what the HF to do if one is Position/Hold and then the music stops.. zero feedback. No further clearance.. time passes.. sweat trickles down the collar.
I would suggest the fix for this is NOT to eliminate P&H, but to put a time limit on the hold duration, in some unambiguous manner. Either specify a hold duration, or let the hold automatically expire into a departure after, for example, 120 seconds -- unless HOLD is renewed --, or at least define the situation as 'all bets are off' 120 seconds after the clearance, so aircraft holding must take the initative to obtain further info, and failing success in that...clear the runway in the best manner possible.
Useful procedure. Needs some procedural disambiguation.