Ahh, now we're getting somewhere. I too see the computer as a tool, and I like to get the most use I can out of the computers I collect. I can even reasonably see upgrading as a viable way to get more use out of a computer. But whenever I upgrade my, say 5150, 5170, or any other vintage computer, I upgrade with parts available at the time or reasonable replacements. I don't believe in putting VGA video in any 808X computer or 286. Those processors aren't strong enough to get any real difference between EGA and VGA. Now 386's and up could come with VGA or VGA was readily available, and they can run programs optimized for VGA.
There are few exceptions to my belief. For instance, if VGA is put in an 8088 5150 for some cool project, such as making a video on the 5150, or to get 256 colors on a 5150 to paint a picture, or just for cool factor, I see no problem. Just the same, if no CGA or MDA monitor is available and VGA is the only viable solution, I'd put VGA in an 808X as it's better than nothing.
Another upgrade I can see reasonable is replacing an MFM drive with an SCSI drive. SCSI is far more reliable, and when you are like me and store VERY IMPORTANT DATA with your vintage computers, you want something reliable to fall back on if your floppy disk is damaged. It happened to me before. My floppy disk I had my important data on was destroyed. So, I figured I'd just load the backup of the files I had put on my MFM HDD the day before. I fired it up and the MFM drive crashed. I never saw that financial report again and had to start anew with a new, better system. But if I were to put SCSI in my vintage computer(I haven't found a good card yet) I'd make it LOOK like MFM. Another plus about SCSI--CD drives. Their not genuinely vintage, but they are still great for opening your vintage machine to huge amounts of information without huge amounts of floppy disks. For instance, the 8GB of DOS games on my HDD would be a pain to put on disks. Just unzip them onto CDs and I could play any game I wanted to without an infinite amount of disks.
Now my post is very long and hard to read. I will stop soon. Point is, I don't think vintage computers should be upgraded much more than what was available in their hey-day, with very few exceptions. It's like taking the 8-track out of a muscle car and replacing it with an MP3 CD player. Blasphemy.
--Jack