CD4 Tcells are responsible for secreting many different cytokines for regulating cell differentiation in the bone marrow, for instance IL-3, stimulates hematopoiesis, Il-5, stims growth and differentiation of eosinophils as well as B-cell growth, IL-7, stims pre-B and pre-T cell differentiation and production, and this is just a basic list. CD4 T cells CONTROL the immune system through chemical cytokines, and losing the CD4 cells leads to either (1) no immune response or (2) a completely inappropriate immune response, because the CD4 cells regulate the response of other immune cells.
Also, most retroviruses have similar replicative cycles and analogous events to your 1 - 9 occur. Why is HIV cytopathic whereas others are not? Is this known? Is it believed to be mainly CD4 related?
The reason for the "lag" from time of infection to time of aquired immune dz probably has to do with the fact that some cytokines have slightly overlapping functions, and the body, being cleverly made by God, is able to keep up a defense until such a time that the CD4 are sufficiently depleted that it matter not what other cyctokines other immune cells are producing, and yes, HIV is CD4 specific.
All right. This is not direct, but indirect.
You also know that this is wrong. Completely myeolablated animals are able to be recuse and reonsititute their blood system by stem cell enriched bone marrow extracts. Cytokines are produced that regulated hematopoiesis in the marow stromal cells and also osteo cells.
CD4 cells are not necessary for hematopoiesis.
I'd say if there were a cytokine that didn't have overlapping function it would be the exception. This is hand vaving, which is fair enough, but is again away from the direct cytopathicity of the virus on CD4 cells.