Well, i think for PFTP i'm going to make it so that if you start typing while an FTP window is active (but the directory string gadget is not active), it'll select all matching files.
Like, hit "A", and all files starting with A are selected, then hit "N" and all files starting with AN are selected etc. etc. and hit ESC to clear the selection.
As for an OS3.x port, maybe. There are a few potential snags there; first is that i'm using the AmiTCP socket signals API (since i prefer it to WaitSelect()), but that is buggy in some OS3.x TCP/IP stacks. As i'm writing for OS4, i'm assuming that it works since OS4 ships with roadshow (where it does work).
Second, i'm using OS4-specific features, like SFTP support relies on some OS4 extensions to queue-handler (and specifically requires Steven Solie's OS4 OpenSSH port). I'm explicitly using interface pointers, mutexes, extra gui pens, new features of reaction, 64bit filesize compatible DOS operations, extra process management features...