Not related to your question, but (the original) cron uses the editor defined in the EDITOR environment variable. So you should be able to change it by first executing e.g.:

export EDITOR=/usr/bin/nano

Regarding your question: have you tried setting up a cron job for "user" (e.g. crontab -e -u user as root; or add user to /etc/cron.allow or /usr/lib/cron/cron.allow (if in doubt, grep allow /path/to/cron) then run develsh as user then crontab -e)?