1) Kai's ASGR is unmodified- all of Origin's GR-series rifles (even the GSR, though it isn't recommended) can mount a SLAG.
2) The Daisy II also does not need any modifications to mount the Missile pods, and can mount them normally The GEP, as it is written, doesn't have any way of automatically feeding ammuinition to anything other than the 50MM Gauss bazookas, and unless set up for that purpose, lacks the hardware and is otherwise just an armored box. You can fit extra ammo in it, but I don't really have any good way of figuring out how big the thing actually is. Also, if you check ammo capacities between the LASR and ASGR, the Daisy II's thigh compartments can actually hold more ASGR ammunition. 1200 rounds for the ASGR vs. 800 for the LASR (this is due to the configuration of the magazines themselves)
As for the GEP itself carrying more ammunition- it can be used to store more Magazines but you kind of have to pick one thing to stick in it and stay with that.
3) the ASGR is a good all-round rifle, which makes sense for just about anyone. also, the Missile pods for shoulder use are offensive, which means they do actually explode in the traditional sense, and can theoretically be used for Demolitions. I would also suggest going through the list of
Star Army explosives and figuring out which equipment you think she might need, and putting that in the GEP, instead.