PBXtra (Not trixbox) AGI

We have a PBXtra system from Fonality which has some different limitations on it and I'm trying to overcome one.

First off, I can't simply modify the dialplan config files. Fonality doesn't allow that. They would get overwritten by the hosted web interface.

That said, I can point an extension to an AGI script. So here's what I'm trying to do. I abhor predictive dialing but still want to make my agents efficient. Right now I have an extension that redirects to "dialout.agi" which is a simple perl script that looks up the CID of the caller, finds the "target" number (i.e. the person we're calling), sets CID to match whatever project they are on as well as dynamically naming a MixMonitor file.

This is working really well. The problem is that I want to initiate a call via AMI that allows me to add SIP headers in (specifically SIPAddHeader answer-after:0) so that the Originated call (from AMI) is automatically picked up on my agent's phone, and the CID that shows on the agents phone is the same number they are dialing.

Make sense?

So far, I've attempted a number of things which have partially worked. The latest idea is to have 2 internal extensions that both redirect - the first one adds in the SIP header for autoanswer then rings my agent, the second dials out to the appropriate target, sets CID, and sets the MixMonitor filename. I can't get this to work.

Any ideas? (bearing in mind, I can't simply modify the dialing plan as a normal trixbox setup would allow)

Thanks!!
PB