Just had the "mbr erased after installing windows" issue at a client's house trying to make a dual-boot, the windows cd they had wasn't viable and led to a corrupt install with no usable bootloader, so there wasn't much to do... Tried reading forums to restore grub2 rapidly, but I finally couldn't sort it out in the short time I had, and had to re-install mint completely ; I did achieve it on my own computer, once, but I had time to fix it by trial and error. The need for a solution to restore the bootloader (grub2 or burg) easily, either from the rescue cd/dvd/usb key or from windows is important.
Could the usb install key / cd include a script to fix grub2, or even install / fix a cool looking bootloader like BURG (if it's stable enough) from both the install cd and the windows autorun.ini? To a further extent, at-home-system maintainers need various tools out of an installation / rescue CD, like clonezilla (to make system / partition images that could be put on an usb key), or an anti-virus to check files on the windows-to-be-repaired, or other software that are generally included in a rescue cd (like ubcd or hiren's), most of them open-source. Could a cd image prioritise those "rescue CD apps" and compensate the shorter space of the cd by downloading the additional apps and codecs during system install or after initial install? Being a good platform as a rescue cd (for techies) seems to me to be important for an install cd and could help mint get known. Having just another question at the end of system install to ask which apps I want installed and then downloaded may be a nice idea, if there's a default button for newbies, and a custon checklist, or even some preset app selection buttons (server, multimedia, education, scientific, etc.) for techies.
Size-wise, such a question doesn't apply to a dvd image : it could even could carry both cinnamon (default for the traditional desktop and live cd/dvd/usb key), unity or mate (default for tablet / touch), LXDE, Gnome3, KDE, (and even (if you're evil) an M$metro to show how linux performs kernel-wise compared to M$), etc. and ask us, during install, which environments we want installed (and even give us thumbnails or a preview of each environment).
As I mentioned on previous posts, if the medium is a USB key (which is more and more the case), the possibility of making this install / repair tool save the downloaded apps and locales to the usb key during install (so that it doesn't have to during the next with the same medium, or even copy this updated install medium on to other usb keys) could make mint viral.