Inodes mean no. of files/folders you have hosted on your account. So, removing inodes means removing files/folders from your account. If there are any useless files on the software you are using, you can delete them. Otherwise I don't think you can do anything else.
Infinityfree is already doing that. On infinityfree 3 active accounts are allowed means if you have 3 account and 1 of them is suspended, you can create 1 more account but after you create another account, you cannot reactivate previous account.