For me too, your point of view is interesting (and surprising about DeltaGlider)... can you elaborate a little for this "training sequence"? Maybe also suggest some key-Addon for new comers...
Sure.
The DeltaGlider is great for practicing just about everything in space, up to and including interplanetary trips.
Plenty of fuel, maneuverable, loads of dV, docking port pointed forward, etc.
Example, if you mess up a rendezvous, there's plenty of capability to fix things with brute force.
However, the aerodynamics model is not good for reentry. Certainly not in any way realistic.
Addons like DarkEnergy or Crew Dragon, depending on the user's preference for capsules or winged vehicles, work for reentry in a realistic manner and they come with autopilots for reentry so you can learn by watching an autopilot fly before trying to fly a 5000 km hypersonic glide yourself.
However, they have realistic dV budgets and relatively low thrust, so they're not the best vehicles to learn orbital maneuvers on.
I think for newcomers, I'd suggest avoiding loading up on a bunch of addons at first.
However, some stuff is almost a must-have: (All found here on OF)
- D3D9 graphics client
- Lunar Transfer MFD
- IMFD
- BurnTimeCalcMFD
- Some kind of launch vehicle (Falcon 9/FH, Ion LVs family)
- Crew Dragon or DarkEnergy spaceplane for learning reentry
- I'm sure someone will tell me I missed something important on this list...