Since December, 2016, Helpjuice supports accessing multiple accounts with the same user/email. However, each access has to be requested to Helpjuice team. If you want to allow access to an account, get in touch with us via chat.
Once the access is configured by us, the user will start seeing a switcher:
We can add multiple accounts to the same user, but the account owner must approve the access.
Be aware that we do not support different roles for each account. If an user is an admin in Account 1 and has access to Account 2, he'll be an admin in the latter too.