Most Building Officials consider sliding doors as doors that take “special knowledge” on how to operate. (Latches and locks and pulling a door in an emergency appears to be too confusing. See ICC R310.1.4)
In order to replace the concrete wall, you have several issues: 1) structural replacement, 2) disturbing existing soil conditions, 3) point loads from new end posts at windows,
Providing a structural wood wall where a structural concrete wall was installed will take a few calculations, which will require a structural engineer or architect to become involved. Also involved will be shear forces due to seismic activity or high wind, if any. (The house will want to “rotate” under those loads and that load will need to be transferred to the side walls or down to the existing footing.)
Every building settles during construction. Partly due to adding the weight of the building materials and partly due to disturbing the soil and it re-compacts over time. Leaving the existing wall will eliminate this effect.
Installing new header and end post locations will cause the load to a new location along the wall. Where this new load transfers to the footing will need to be calculated, sized and increased… no doubt. That could be expensive.
The Code requires “Emergency Escape and Rescue Openings” in every sleeping room. (See ICC R310.1) However, it does not require a window. You could install a “swing type” door.
If the two sleeping rooms are side by side and where the existing slider is located, you could install the doors in the existing opening and then fix the sloping ceiling/ floor. If that does not quite work, you could install a one-hour fire rated corridor from each bedroom to the new swinging doors. (However, you’ll still need another bedroom door to the basement area AND written approval by the Building Official.)
Obviously, any structural change will take a Building Permit. However, if you just add new doors, then it’s not structural. (I’d let the Building Officials know it’s “maintenance”, which does not require a Permit.)
Remember, those egress windows work both ways. They’re for the occupants to escape, but also there for fire fighters to look in and see if anyone needs help. If you talk the Building Officials into the one hour corridor, you’ll also want a window too… just to see the sun and visual connection to the exterior.