I think every decent hosting provider on WHT should have this feature if have same control panel in both end .You can transfer cpanel-cpanel ,directadmin to directadmin without any issue or ask the same with reseller provider .
Just to clarify, are you perhaps talking about the feature to upload and restore backups yourself?
I think the OP is talking about self-service type restores/migrations from within WHM as they said "eleven2 doesn't" - that would lead me to believe they're talking about inside WHM since Eleven2 and most other companies do perform migrations.
I don't think you're going to find many, if any at all that allow resellers to restore accounts. It requires root access & can end up being problematic along with the security concerns...
There is a tool in whm, however it does not do a complete account transfer, ie: settings etc. Its likely easier to upload the full backups to the home directory of your main domain and ask the host to restore them for you.