Is it possible to change the stellar classes within Celestia?

[Joey P.]

As we all know, Celestia uses the main Morgan-Keenan classes (B, A, F, G, K, and M) and the extended classes (W, O, R, N, and S or C). But is it possible to change or add classes in the system in Celestia, regardless if the outcome will be scientific or not? Why not have Celestia using the old Draper system (classes (W,) O, B, A, C (not Carbon star), D (not white dwarf), E, F, G, H, I, K, L (not brown dwarf), M, N, and P (planetary nebulae) and Q for miscellaneous). Is it possible for Celestia to have all those classes?

Added after 2 hours 40 minutes:
Here are textures (not by me, but by fizika) for star types H and I, G, E and F, A and D, and B and C.

[Joey P.]

Textures for W, Q, O, N, M, and K and L type stars.

Added after 5 minutes:
What I think is the best default texture of type P's nebulae: