It's called a _SCANDOUBLER_
they were invented years and years ago and you can buy them from all good Amiga stockists
As for being able to do it with 3 IC's, I wonder which ones they are or how much they cost? Probably cost more than a traditional Amiga scandoubler.
Remember you are going to have to buffer an entire field
of data if you want to flicker fix as well as scandouble which is a fair few kbytes for the highest resolution AGA interlaced screen.
Most scandoublers dont work with the majority of LCD monitors. The vertical refresh of the scandoubled screen will be 50Hz (60Hz in NTSC) and the minimum vertical refresh supported of most LCD panels is 56Hz!