if the collective isn't working
i don't believe it would make any difference where the throttles are!
It sure would to me. But that might just be me. It's the way I learned and the way I practiced manipulating the throttles. Reaching up to the roof or down to the floor might work too, but for me at least, not as well. Point taken though.
Could you give us another option that would allow the safe landing of a "collectiveless helicopter" that would not involve the use of throttles?
Reduce altitude by increasing airspeed, use power pedal and uncoordinated flight (slip) to aid in slowing airspeed before touchdown, find a long, wide hard surface runway with crash equipment, anticipate runway friction to slow you down after initial contact, anticipate ground effect and the possibility of becoming airborne again, be ready to cut power by fuel or throttle(s). Burning off fuel before landing will make you less likely to burn, but should be weighed against lighter and consequently faster landing speed. Use a crosswind / headwind combination to allow you to use more power pedal to rob more main rotor lift. If at altitude, consider that OGE hover requires more power than forward flight. An OGE hover may be a way to lose altitude, but may require you to shuffel in and out of settling with power on the way down. Settling will reduce your altitude but could get out of control if allowed to progress too far. Remember, you can't reduce collective to aid in recovery and must rely on airspeed only to come out of settling. All of the above, by the way, is if your power settings are too high, such as in cruise flight when collective is lost.
If on the other hand you lose collective in a reduced power scenario such as in a decent but still have sufficient power to maintain some forward flight and maintain altitude, your landing might be considerably less challenging.