Pathfinder--
I raced 125 MXers competitively for a couple years and worked/wrenched at an MX shop for 3 years, so I know a bit about them.
While I can certainly see where a bike would be helpful if your GMU allows it, my concern RE your bike choice is one of real world practicality. My comments below are simply direct and blunt. Not meant to be mean spirited in any way.
Pipey/loud, low-torque, light flywheel, small cc two strokers would *Definitely* not be my first choice for trails where you will have sections you'll need to plonk along to get through and potentially steep, rocky/technical sections you'll need to climb through. Nor would I want one where I'd rather be at least a bit quiet and not piss off the game and other hunters. Two stroke MXers have no headlights, nor wiring for it. They are specifically designed for wide open race tracks and designed to run with the throttle at WFO "ie Wide F'n Open". They are not optimized at all to run at partial throttle and you cannot cheaply modify them to do so. The porting, flywheel and pipe tuning are completely wrong. With a 125 MXer, you are either On The Pipe, or not. If you're not it, then you might as well be peddling a tricycle. They have almost zero power/torque when not on the pipe. Their motors and gearing are not optimized to plonk along or navigate between trees/rocks, at slow speed/partial throttle because they have zero power then. Nor are they optimized for someone intending to add panniers/front racks, etc.
Yes, you could lower the final drive gear ratio by changing sprockets. It won't help much. With a 125 two stroker, you'll have to get the motor "on the pipe" to get horsepower and everything and everyone around will know it. And when an MXer is On The Pipe, the rear wheel will spin like hell and dig up the trail or road. Even if you only stay on gravel roads, pipey 125 MXers are rudely loud and low powered slugs when off the pipe. And what will you do for lights?
You may want to strongly reconsider, take your lumps, drop that bike to another buyer and get a 4 stroker with a much larger motor, a good muffler and a real headlight. Modern 4 stroker motors are pretty darned light, have heavier flywheels and far more forgiving in the types of scenarios you will encounter. They have more torque than a 2 stroker, a broader power band and they will let you more easily navigate 99% of what you'll run into. They also have a greater cruising range and they are quieter by far.
My 2 cents. Best of luck with your path.
JL