A couple of things,
First, Smallflame, I take it you are a volunteer for SAAS going on your post. In regards to your post, and the responsibility thing, age should be no barrier, as I have met some young people who are very mature and responsible, and others who are older, who lack maturity and lack a whole lot of responsibilty. In your role, yes you can administer certian drugs, but only under specific guidelines and after a consult to an ASMO, Penthrane, salbutamol and oxygen excepted.
In regards to being able to distance yourself from "gory stuff", well I think no matter which organisation you work for (or your case volly for), there is always potential. And, what some people call gory, others won't.
As for the more experienced paramedics in metro,you need experienced paramedics in country too, considering that there are big distances to cover, and you can get some nasty stuff in country too, not to mention that volunteer crews may (and do) require a higher level of clinical support at times. In metro, you want another car, 99% of time you will get it. In country you want a second car, well you may not get it, or if do, it can take a long time.
As for the retained idea, it could work, MFS to it in country, and it works well. In SAAS's case, well, it could be an option, but not up to me to make.