Maybe he wants to go 4:3 to 16:9 in an elegant way. 😉 I’ve not done a conversion like this but it does sound like an idea that’s worth a try.
FWIW, InstantHD does a decent job starting from SD 4:3 to HDs 16:9. Once in HD, it’s a matter of scaling down to SDs 16:9.
The nice thing about InstantHD is that it handles PARs very well going from non-square PAR SD, to square PAR HD.
Cheers
Roland Kahlenberg
https://www.broadcastGEMs.com – Adobe After Effects project files
https://www.myspace.com/rorkrgbspace