Yes, I totally understand what you mean. I plan to revamp the "+" button in Textastic to let you create a new, untitled text document.

Would it be ok if this always starts out as a plain text file (you can change the syntax in the File Properties popover) or should there be options for other kinds of files?

Textastic 8 will have an option to ask for the password when connecting to (S)FTP servers.

Textastic 8 will support ECDSA and Ed25519 SSH keys.

Textastic 8 will allow you to select any installed monospaced font. You can use apps like AnyFont or Apple Configurator 2 to install custom fonts.

This will work again in Textastic 8.

This will work in Textastic 8.