Question : VOIP setup for ships

Hello:
We have 22 ships with about 50 people on each ship. Some of these folks spend 255 days out of the year at sea. So, VOIP would make over 1000 people very, very happy.

Each ship has a PBX that has open spaces for anolog trunks. Being government, they want to be their own ITSP. The ships are in about 5 different time zones and the phone lines will not always be in use by all ships. So, this is what I am thinking:
1) I think 24 analog lines will be nice as a backbone for all ships. So, have the phone company d-mark 24 pots lines at headquarters.
2) At headquarters, have those 24 voice lines go into a 24 port VOIP gateway, if one exists.
3) It will go over existing KUband and C-band satellite comms that provide us with 24/7 internet. (In fact, that is what I am communicating with you on)
4) on the ship, have a four port gateway for 2 analog and 1 fax that plug into the PBX.

So, this is what I am asking of you:
1) I have to do a feasability analysis. Is this plan feasable with the structure I have laid out or am I missing something?
2) I have to do a security analysis: How can we make these as secure of connections as possible?
3) I have to do a cost analysis: Can you recommend any products to get this done because I have to do a cost analysis?
4) I wish to provide alternative or working solutions: Would you recommend an alternative plan.
5) I should do a bandwidth analysis: Bandwidth is limited, can we keep it bandwidth freindly? ->>We tried skype on one PC before headquarters considered it a security risk and it used 10Kb/S. (Very Nice)

Just use one ship as an example and we can copy/paste the setup to the other ships.

GUYS/GALS:
If I could make this worth 800,000 points I would. I can't tell you how much I will appreciate your help.

Answer : VOIP setup for ships

The 24 lines don't have to be doled out to specific ships. They represent a pool of lines everyone shares. And you can get as many DIDs on a T1 as you want -- they're not tied to the lines. I support an installation with 150 people  in ten buildings, and a single T1 works just fine, and these are all desk-bound people on the phone a lot.

The DID's generally cost something like fifty cents each per month. When a call comes in on any of the DIDs, it takes the next available T1 call slot, goes to the VoIP router, get's routed to the appropriate destination phone based on IP address, and you're done. Outgoing calls use T1 channels from the other end of the pool (e.g., starting on channel 24). It's very easy to expand these systems to two, three, or four T1s, should you outgrow the single T1.

The primary controlling cost of the T1 gateway is the number of dedicated DSPs for digitizing voice streams. Generally you need one per T1 channel you want to use.  

As far as I know it's OK to ask. I'm new to EE, but a long-time VoIP engineer on the West Coast near Pt. Mugu Naval Air Station.

 -mel