I think that the reason stage0 and other projects work this way is that they found lisp and other projects to be very limiting and there were definitely some reasons that they do things the current way that are mentioned in their docs.
I had this thought once that there would be a single sd card or hard drive which would allow bootstrapping source and a hash and with systems like tor and torrenting in general combining with self hosted wikipedia perhaps and all the mirrors of open source software I use.
I had this idea that its now possible to have such hard drives if I so desire and I am not usually paranoid but in actuality, feats like bootstrappability remove paranoia because I feel like there must be other people who do this and who verify security and I can always go to them or they exist :)
Bootstrappability is really cool and awesome stuff in my opinion which is severely underrated by many and I am glad that people like you work in helping bootstrappability. Have a nice day!
Regarding the comment itself, I didn't know that this was the case of Mes as I had just thought the only thing it depends on is scheme but thanks for sharing information about this.
So, you need a minimal C compiler that can also compile the ungz and untar programs from their C sources. At the moment, I have a minimal C compiler that can compile the Tiny C Compiler and the standard library that is part of the GNU Mes compiler. One of the following tasks will be to see if it can also compile the sources for ungz and untar, which can be found in [0]. I think it will be not so hard as these sources already have been adapted to be compiled with a minimal C compiler.