[sciurius]

It would be very nice if MSPro would provide support for producing chord charts. However, I fail to see how this would be possible from ChordPro without affecting the elegant simplicity of the format.
For the past 25 years I've made numerous attempts to write chord charts in existing tools. None of them could produce anything satisfactory and that's why I wrote playtab. Nowadays there are some iPad/Android tools that can produce something similar (e.g., iRealPro) but, just as you point out, you give up at least one of niceness, maintainability and transposability.
While introducing horizontal tabs and using a monospace font would give ChordPro some abilities for alignment, it will be limited and you'll become disappointed soon. For full flexibility you'll need much more control than just tab widths, requiring several other directives. To give some examples: You'll want to label sections (Intro, verse, vamp, coda, ...), add playing instructions, and so on. Control vertical spacing to separate sections. See the attached example.
Therefore I already suggested to not treat this as something to be shoehorned into ChordPro, but as a distinct data type. This would give all the added values of MSPro (e.g, organizing into collections and setlists, building indices, performance display with transpose capabilities).

As for the hor_tab proposal: it's a start but it has a couple of drawbacks. First, what you really want is columns. For example, the attached song would have 4 x 4 colums. Second, tabs are invisible and vulnerable. An editor or an email program may replace them with spaces, or you may have one tab too much or to less and you won't notice easily. That's why I use a "visible column spacer" (a period) in playtab.