I bumped into a possible loophole in DA account limitations that may be worthwhile looking at. I only did brief testing and am initially taking the 'lazy way out' by notifying you guys and leaving it to you to have a look at.
Recently I moved a user to a DA reseller account at a third-party and there were a few options within that reseller account that are more limited than user accounts on my own servers. When I restored a back-up of users from my own server onto the 3rd-party server (with stricter allowances), the user got some of the allowances from the server where it was backed-up!
I got triggered in particular by the subdomains option at the 3rd-party, since in that reseller account (and subsequently all other users there) it is not allowed to have/make subdomains (subdomains=0), don't ask me why
. I didn't have the link to "subdomains" at the "your account" section when I added a new user. I restored a couple of users from my own server as a test and lo-and-behold: they now had the "subdomains" option! Looking at their config, they are also allowed to make subdomains (where new users are allowed to make zero/none!).
So basically, the settings in the restored back-up at reseller level overrule this reseller-account limitation, set by that 3rd-party provider. I have not tried to see what happens when users restore a backup at user-level with modified settings. In theory, if this also overrules the local limitations, you could hack the settings and give yourself a bit of 'extra'!
Lastly, I have no idea what will happen when a user is 'allowed' (through modified backups) to use more resources than the reseller account is allowed. Maybe DA will limit the resources through the reseller. However, since the subdomains work, and new ones can be created under the restored users while none are allowed, it suggests that at least some resources are not checked strictly.
I emailed DA a while ago and received no response, so it might be a non-issue. Certainly, as long as it is only the subdomains setting that is affected. However, when diskspace, email/mailinglist accounts, bandwidth, etc. can be modified this way, it could be more of a problem. I am interested to hear your first impressions on this matter.
Recently I moved a user to a DA reseller account at a third-party and there were a few options within that reseller account that are more limited than user accounts on my own servers. When I restored a back-up of users from my own server onto the 3rd-party server (with stricter allowances), the user got some of the allowances from the server where it was backed-up!
I got triggered in particular by the subdomains option at the 3rd-party, since in that reseller account (and subsequently all other users there) it is not allowed to have/make subdomains (subdomains=0), don't ask me why

So basically, the settings in the restored back-up at reseller level overrule this reseller-account limitation, set by that 3rd-party provider. I have not tried to see what happens when users restore a backup at user-level with modified settings. In theory, if this also overrules the local limitations, you could hack the settings and give yourself a bit of 'extra'!
Lastly, I have no idea what will happen when a user is 'allowed' (through modified backups) to use more resources than the reseller account is allowed. Maybe DA will limit the resources through the reseller. However, since the subdomains work, and new ones can be created under the restored users while none are allowed, it suggests that at least some resources are not checked strictly.
I emailed DA a while ago and received no response, so it might be a non-issue. Certainly, as long as it is only the subdomains setting that is affected. However, when diskspace, email/mailinglist accounts, bandwidth, etc. can be modified this way, it could be more of a problem. I am interested to hear your first impressions on this matter.