Mesh11sd initial configuration problem

If it is for next to nothing, then go for it.
You would of course generate a custom 25.12.x image in the same way as before.

If a mesh node is not doing anything else but mesh stuff, even a lowly 10 year old ramips travel router can do remarkably well, greatly helped because mesh11sd does a lot of wireless tweaking over and above what is usually available in the config file.