Overcoming sole founder/key man risk perception?

I’ve been working on a fintech startup for the last five years. The business has been bootstrapped from personal resources and part-time consulting and we’re now cash-flow positive, great reviews from our users, have good reference sites and so on. The company is basically two people – I do all the development and a colleague handles marketing.

Because of the way the product is designed (basically a set of libraries with a simple API, lots of examples, detailed wiki) post-sales effort is fairly minimal and is typically about methodology, occasional technical questions, etc. We can probably expand by a factor of ten before having to take on any support staff.

A problem we’re currently experiencing is the perception of key man risk. A large client in London loved the product, but we were shot down because of perceived ‘key man risk’ – if I were to go away who would provide support? They went with another product that cost 20 times more, was inferior technically, but had large support teams.

So far we’ve addressed this question by offering source code in escrow, so that if I were hit by a bus the client would have access to source code. We could raise some money and hire a support team, but that seems premature given our current requirements.

Has anyone else had this issue, and how did you handle it?