Here are few suggestions:
Squid:
Proxy authentication per user or group? (using samba or mysql)
Web-based squid log analysis (in the e-smith manager)
Url blocking/filtering
Qmail:
Content filtering (filtering of attahment ie movie clips, exe's etc)
e-smith Manager:
ssh terminal (like webmin)
Display the e-smith version (or an about page?)
Service manager page (start, stop , restart, configure)
Apart from that..... GREAT PRODUCT!
BF