I guess you're quite to the point with all you said. Probably the worst logical problem is that an armel-thumb architecture is supposed to also accept armel binaries, but an armel architecture mustn't run armel-thumb binaries. I don't know if that problem can get fixed with a patch to apt or HAM, or by pathnames/URLs in repositories plus symlinks or hardlinks, or whatever. From extras-assistant and midgard I expect the least problems, it should more or less boil down to a duplication of existing cmdlines or dirs or both (given the new 4.7(?) gcc is compatible to the one used now, on the level that it is enangled with the whole autobuilder process).