Hmmm.. your topic is about UPX and the problems it has with 4.5 and I see several references to UPX and the problem in that topic. As for your question, "does anyone have a reason not to use an executable packer like UPX" the answer pretty much depends on why you feel the need to compress, and the topic I linked discusses several. The topic of bandwidth was also very thoroughly covered, as were other ways to reduce it.
First you said that you just want to make KiX32.exe smaller, then later you shifted topic to wanting to package several files together. So what is the topic then that we are not addressing?
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