Multi-site Security System


So the company I work for having me explore the idea of replacing our 1981 security system.  In new expansion areas of the building there are one-off solutions for various doors, etc.  Everything since the 80's has been piecemeal together.  
We are looking at four sites.  All sites have facility wide fences with independent control access to gates.  Only one building actually has security and cams (but very dated).  I'm not as much worried about the cameras, but I can't get my head wrapped around how to handle the security panels.
The gates are 100-200 yards away.  We want to include some soft of reader (barcode, magstrip, prox, biometric, something).  We do not need thermostat control, but we would be monitoring a few temp sensitive rooms.  Very little automation.  Basically, access control and security.
The kicker is I'm certain three of the buildings can use just one panel; with a possible expansion to the gate.  But the fourth's going to be rough.  I has 4 buildings on prem.  All are far enough away that I would need a separate panel in each one.  I do have access to dark fiber to all the buildings except one; and can get a fiber near the gate.  The gate currently has a copper cat3 telco line.  I have thought about using a few serial to fiber transceivers to help with the distance, too.
Our company is a very DIY company.  I feel I'm almost out of my league and it would be better to get someone in here that can developer a good solution based on experience.  But, I'm just a doer and not a teller!
That being said, I've looked at OmniPro (currently have one at home) and Elk.  I tried looking at Bosch, but their site was extremely hard to read/navigate.
Any recommendations on what I should look for, vendors to explore.  Potential issues with Analog/Fiber Transceivers; or anything else mentioned above?  Just looking for a few rabbit trails to run down and through.
I've used OmniPro in multiple sites. Basically ran expansion boards in a conduit, then hooked it up via expansion. It worked for me, but you may like other alternatives. If you like the Omni, it's possible.
The only concerns is the 1000ft limitation of the expansion boards; the 1000ft for the Access Control Readers; and figuring out how to connect multiple Omnipro systems together over a network for a single reporting location.  Network and communications isn't the issue, it's having one screen to see status reports and alarms.  I've thought about finding some Security Call Center/Reporting software that our night people can use.
From your description, I think a commercial security system is a better solution.  Bosch and Honeywell both make panels that could fit the bill.  For example, with Honeywell Vplex addressable loops, you can run thousands of feet to sensors, without remote expansion boards.
If I were in your shoes, I'd call some professional alarm installers and see what they recommend.
Here for work a few years ago looking for a national contract to take care of card access, fire, alarm stuff looked for a few months and tested a few pieces of software at the home office in the midwest controlling offices in Texas and the East coast.
I did run in to some political sort of issues relating to local building management stuff.  I looked and tried 3-4 companies set ups and software.
I settled on Tyco probably because the tech knew his stuff and was a good teacher to me documenting this project.  I only had issues with ADT testing and poor communcations while testing.  IE: one time during a test mode the fire department did come to our main offices and that happened during a test which sort of ticked me off.
At the time did look at Honeywell but at that time it was all vapor ware and promises and never did get to test their stuff.
The testing was in vivo having the vendors install their stuff in different geo locations and me watching from the head office running the software.  Well then a physical post install sight visit of offices.  Lennar in Texas flunked the test.  Not sure if they are in business any more anyhow.

Really though this all came about because there was no official security department and some guy walked in to one of the satellite offices one morning (he worked for the company) and was having a domestic dispute with his wife (who also worked for the company) and blew her brains out in front of the office staff one morning.