Managed Service Proposition development

I need someone to put together some potential business model (options) for customers to sign up to a managed service provision based on a high end IT hardware appliance and supporting management services.

The proposition is that the customer would prefer NOT to expend capital on the hardware item and instead choose to pay a monthly fee from operating funds that includes the cost of the appliance and all supporting consultancy services for an extended period of three to five years. The arrangement needs to ensure our margins are maintained whilst still remaining attractive and cost-effective to the customer.

The premise is that we can then value add through change requests, service improvements and suchlike. We would offer a range of service levels (eg. Mon-Fri 9-5 coverage vs. 24x7) and seek to recoup our upfront costs at a tipping point within the arrangement.

I'd be happy to work on a "time hire" or "price for the job" basis and would imagine needing to provide quite a bit more detail prior to work commencing - I'd welcome propositions that incorporate this aspect please.