To be frank, as a Sgt/FS in TG17, the chances of you getting a AFCO/MOT post are pretty slim. The AFCO posts are mainly aimed as Cpl's as they cover what used to be known as Case Progress Clks (CPC's). There are TG17 SNCO's currently in AFCO's, however they were employed as part of the uplift last year and they mostly have previous recruiting experience as Cpl's. They tend to be SNCO recruiters, as opposed to OM's and so they report to a SNCO who will be employed in that position. The Area FS's all have previous recruiting experience, mainly as OM's, so again getting into that as a TG17 SNCO is hard.
Getting onto a MOT as a clerk is even harder as they are not seen as core employment for the trade, however it is not unheard of. As has been alluded to, contact the local AFCO and ask to speak to the outreach manager, or get his number, and try and spend a bit of time with them. The drafter may give you a firmer answer as to whether he/she will release you from trade to fill such a post as and when they come up.