Whilst not wishing to move this thread onto a debate about what constitutes "little traffic" in terms of overall numbers and volume of airspace, (See comments previous post), the 'Airspace Reservation' option, should you plum for it, would be NOTAM'd as a matter of course and any self respecting airman, no matter at what FL or in what class of airspace they were operating, would undoubtedly do their utmost to avoid it.
You would not therefore find yourself in the midst of a 'Carrier Fly-off' or being 'buzzed' by a fisheries patrol flight. Should any situation arise where a flight, be it in emergency or subject to emergency assistance by SAR helo or Nimrod, (for example), needed to transit such a reservation, your being in contact with the ATC provider, (Part of the requirement for obtaining a reservation in the first place), would ensure that you were made aware of the situation and if necesary ATC would instruct you, if possible, to temporarily suspend your operations.
Any potential "clashes" of interest would be easily resolved by the powers that be by a straightforward change of date, level or location. If all you need is air and sea, then there's a lot of it out there!!!
Use the contacts suggested by PPRuDe and others and I'm sure you'll get somewhere. Do let us know how you get on.
Rgds
T3