While the desire to eventually be trained as a sniper or pathfinder is admirable, looking for means to set the conditions to achieve that goal while in the recruiting process is futile. Other than processing you for the infantry, no recruiter has the influence to improve your chances of either of those specialties, or any others in the trade. Once you are trade qualified for the infantry and posted to a unit, the unit you have been placed in will dictate your training opportunities and your performance and personal attributes will be the primary factor that influences those choices.
As for Pathfinders or Snipers in the Reserve, I know of no units with establishments for either. While some units may be gaining Recce Platoon tasks under the Reserve Restructure, I have not yet seen any indication that those platoon establishments include hard sniper positions. The Regular Force exerts considerable effort to select, prepare and train soldiers for the sniper positions in the line battalions. It is unlikely there is any plan to diversify valuable space on such a course to reserve units when the training is costly (from a Reserve unit perspective) to maintain and would be little or never used.
As for the QOR Pathfinder, that would be a Reserve Soldier who happened to get a Pathfinder course (which makes him probably one out of 5000 or so Reserve Infantry personnel), not a unit with a Pathfinder task and entitlements to regular course vacancies (someone can correct me if I am mistaken). I expect it came about more though the QOR affiliation with CPC, which allowed them to fill a short-notice vacancy, rather than any other means. A known soldier who was already on tasking with CPC at the time perhaps?
And with the Regular battalions, even at 18 hard sniper positions each, that only means 162 positions and probably not many Privates among them. Once established they'll probably have about a 25% turnover annually for all causes (remusters, releases, promotions to appointments back in rifle companies, etc). That means the Battalion may need about 5 new snipers each year out of the 300+ soldiers in the rifle companies. With the reduction of the Combat Support companies, there are fewer jobs outside the rifle companies for all soldiers to desire and pursue, so competition will be strong.