The external server(s) are used as deployment servers and support
FTP, SFTP, SCP, & Web services. That said.
1. Yes
2. Depends on the actually hardware that you are using for deployment server(s).
As long as the External server is configured for FTP, SFTP, SCP, & Web Services,
it shouldn't matter but for 5.1 32bit would be a safe bet.
3. No redirection, HA, or clustering. Manual or Automated Monitoring of the external servers
will be needed to ensure disk availability. You could use multiple servers for deployment file
types to shared the disk load over servers.
T.