Let $\lambda$ be a limit ordinal, and let $F: \lambda\to \mathcal{T}_*$ be a diagram of pointed spaces with shape $\lambda$. Write $X = F(0)$ and $Y = \mathrm{hocolim} F$. I believe it to be true (I have a sketch of a proof) that if
- every $F(\alpha)\to F(\beta)$ is a the inclusion of a sub-CW-complex, and
- for every $\beta < \lambda$, $F(\beta+1)\hookrightarrow Y$ is homotopic, by a homotopy constant on $F(\beta)$, to a map that factors through $F(\beta)$
then the induced map $X\to Y$ is a homotopy equivalence.
This is certainly very classical in the case $\lambda = \omega$, but I would like a reference for the general result.