Take a look at Intermedia, from what I can tell they are a favorite of VARs and are also in the Ingram Micro cloud catalog (along w/ Box). Xero also has some level of reseller relationship with accountants but that is more than just a typical VAR or disti model, since the accountant remains deeply involved with the business client.

One issue that VARs brought up in my discussions with them was branding - they really like to have their brand in front of the customer (this is one of Intermedia's selling points). Not sure if this would work for you or not.

Happy to jump on a call to discuss more, I spent quite a lot of time looking into this at my last company as we launched a SaaS service.