Thanks...sounds like a good project
Who is teaching you about rope installation? There are several thowline shooters available. More important is understanding how to qualify a TIP..tie in point. Since this is for rescue you're likely going to have to consider a two person load on the TIP..plus amplified shockloads.
What books do you have?
The Tree Climbers Companion
TCIA SRT manual
Last week I was going through my bucket of ascender/descenders. One tool that isn't used much anymore by arbos is a t-bar foot ascender. For your needs I think this would be much better than the rope walking systems arbos are using these days. RW's are complex and need to be tuned in order to work safely. A sit/stand setup would be easier I think. Then, change over to a descent system when you get to the victim. In that same bucket are a couple of descenders that can be adjusted for one or two person loads. Fast or slow descents. They've worked really well for me when I've climbed west coast big trees.