Please let tycho-p2-extras-plugin support mirroring a repository using its mirrors

[Baytars]

I need to mirror a repository (A, https://download.eclipse.org/xxx/yyy). However, I don't want to access that repository because the transfer speed is slow. So I turned to <mirror> tag in pom.xml, only to find that the mirror (B, https://mirrors.aliyun.com/eclipse/xxx/yyy) only takes effect for those repositories written under <repositories> in pom.xml.
Mirroring a repository (A, https://download.eclipse.org/xxx/yyy) using its mirror (B, https://mirrors.aliyun.com/eclipse/xxx/yyy), sounds like a brain-twister, right? But please imagine a scenario: we are going to mirror B directly using tycho-p2-extras-plugin, instead. However, mirror B is a composite repository that refers to other repositories under the same domain name as A (C, https://download.eclipse.org/zzz/kkk). We would also like to mirror C using its mirror (D, https://mirrors.aliyun.com/eclipse/zzz/kkk). If the tycho-p2-extras-plugin supports mirroring, life will can be a lot easier. Do you agree?

[laeubi]

I must confess I do not fully understand what should be archived, would it be possible to came up with an example project instead of all these A, B, C, Ds?