Wireless phone system - HF Radio using PPP with VOIP/IAX2/MELPe would be extremely cumbersome to setup, but is doable (might require bonding which makes it even crazier). MELPe is a military codec operating at 600/1200/2400 bps. With PPP/IAX2 you have very little networking overhead. The quality of MELP is hard to describe, but with carefully tweaked jitterbuffer settings, cell phone quality should be possible. The advantage is that you avoid the annoying lag. This setup would require an extremely hacked Asterisk.
Paging system - "Smart system" where everyone wears a transponder so the communications system knows where to page/ring you?
Fire/Life Safety systems - Detection and Warning
Entertainment - Internal Fiberoptic network to move large quantities of data - movies, etc? Cable TV analog
Satellite Entertainment TV/Radio
High Frequency Radio - 2-30MHz
Worldwide Coverage, very large antennas (30+ meters long, or longer?)
Possible 'Pirate' Radio Station(s)?
GMDSS System Global Maritime Distress Signal System, SOLAS requirement
VHF-FM Radio Marine Band 156-158 MHz SOLAS requirements to maintain a listening watch on distress frequencies
Coordinate small boat activities around SeaStead, each small boat equipped with one of these too.
Relatively small radios, low power (~25w ERP), small antennas (2 meters or less in length, max. Handhelds ~8" long)
VHF-AM Radio Aircraft Band 118-136MHz
Coordinating air traffic inbound and outbound.
Several frequencies: Departure/Approach, Tower (landing), Ground (ground movement), coordination frequencies
Air Traffic Control radar
Tactical Radios - Trunked 800 MHz systems? Used for:
Firefighting / EMS
Need to investigate frequency propagation through structures.
Other radios - Ability to monitor/speak on military frequencies, ie
30-70 MHz FM (Military Tactical Net);
220-400 MHz AM (Military aviation band), etc?
"Company" radios for SeaStead operations, similar to business-band frequencies (VHF-FM High at 150MHz or UHF-FM at 450-470MHz and/or 800 MHz trunked system. Will probably require robust encryption.