I would suggest that you use a tricolour combined with anchor light at the masthead, if only because of the significant saving in current
draw from one lamp over that from 3 individual lamps. You can also get these as a tower, combining strobe if wanted (which we have but only for the potential use that Wotname mentions, so hopefully never used), tricolour (side and stern lights together from one lamp), and anchor all round light.
For motoring you are not allowed to use the tricolour so one still needs red and green on the pulpit, motoring light on the mast, and stern light on the pushpit. However, if these are switched with red/green/stern lights on together, and motoring light switched by itself, you end up with a spare set of nav lights for sailing if the tricolour lamp fails as you can just use the red/green/stern lights. If you have both house and cranking batteries you have redundancy for sailing nav lights including their power supply (here in NZ foreign going sail boats on the NZ Register are actually required to have redundancy in their nav lights).
You should have no problem fitting the usual sensors and antennas at the masthead. We have nav light tower (tricolour, anchor, strobe), VHF antenna, wind sensor and windex no problem at all - the wind sensor and windex are typically off stalks fore and aft off the masthead fitting, the VHF antenna on a side mounting bracket so the only masthead fitting real estate used is for the nav light tower which takes up little room.
We do not carry lightning protection but the very undersized protection that is fitted on other than large sailing vessels takes up little room.
Other antennas do not need the height - our cell phone
antenna is under the solid dodger
(height is an advantage but can be quickly set off by transmission
line losses in the coax at the near 1 GHz frequency), TV, AM/FM, GPS
, spare VHF at the pushpit (which would serve as AIS
antenna if we carried AIS, which we currently don't do - results show sufficient range for AIS off a low antenna). TV can usefully be carried on a spreader for height advantage as long as it is an active antenna but we have not bothered as we only use the TV when in harbour - for non metal boats an internal antenna may prove sufficient. We kept the active TV antenna a couple of feet away from and a bit higher than the GPS in order to minimise any possibility of any spurious radiation from the TV antenna's amplifier interfering with the GPS one.
We carry our radar reflector (Davis round octahedral) on a halyard
to the port lower spreader matching the flag halyard
on the other side (but usually don't bother with it as we are a metal boat) out close to the shrouds about which there is a stabilising loop from the halyard to stop swinging. Another thread indicates that low may be best. Davis used to do a very nice halyard suspension fitting to enable this and that is what we use, but I think they may have discontinued it.
antenna is a end fed wire craftily placed just behind and inboard of the shrouds on the starboard side so it is protected from the genoa
and heavy weather
and on a halyard to the upper spreader. The tuner is immediately below behind the nav station cabinets. I did trials against my antenna tower on land and decided that the proximity of the rig on MF/HF was no worse than the back stay would have been and seems to have proved so (I have worked other mobile stations with non gain antennas, even cars with short antennas, on the other side of the world on 20m band). However, if you have a low freeboard boat where the deck floods and wish to operate at the same time then the only place to rig the antenna is at the stern so the through deck insulator can be mounted on the transom away from seas.
Our boat is larger than yours but as you can see, the amount of space used at the masthead has been small and would be no problem on most any small boat.