@burke,
I understand your 'unified logic' idea but this doesn't ALWAYS apply in software. Even you say it 'has pretty unified logic'. That implies that it may not be the same throughout. My comment on that is derived from the '101 on keymaps' section of the official XBMC forum asking the user to download a complete 'keyboard.xml' file. I took this to mean a user needed to download a complete one in order to change something. Fortunately, that is not the case. Creating a 'keyboard.xml' file and changing one function does nothing to the rest of XBMC's built in mapped keys.
Your mention of my future "how to" is for XBMC users in general. Flirc is not a requirement. A keyboard is not actually required for this but at least some input device that could send keyboard commands to edit the 'keyboard.xml' file: ie. an on-screen keyboard (Android, iOS). Editing the 'keyboard.xml' file is to change the default keys to function with different keys. For instance, the MCE Remote sends the keyboard equivalent (CTRL + SHIFT + P) to play a video. You could edit the default XBMC key of 'P' to be the same as WMC's and now your remote can control XBMC and WMC's 'Play' function with the same remote control keypress (since they are mapped to the same key combination).
If you use "standard ir", as you say, there is no difference. The 'ir' device sends some signal that is interpreted by the receiver as a key press function. If you determine what that key combination is, you could edit the 'keyboard.xml' file of XBMC to match this command and now your remote is controlling XBMC. It doesn't matter if you buy a $12 remote/receiver combination, or are using a custom LIRC script, it will work. In this case, the device sending the keystrokes is Flirc.
There is a great little bit of code called 'ShowOff' that will display the keys hit (or sent by any ir device) by way of an onscreen display. Very tiny and no installation required.
I may check out the 'addon' but I'm not a fan of additional software to do something I will probably only need to do once. I'm the 'tinkerer' type.
Have fun...