I think that the problem with offering this type of service to domain investors is that it's difficult to monetise the service provision.
If you offered it on a profit share then you'd really only want to develop the better names (ie ones with good potential traffic and commercial focus), as every domain takes a similar amount of time, and then what's to stop clients using the service as a "leg up" to get into SERPs then changing the DNS and self developing later on? Maybe some sort of contractual obligation or 2 way service contract?
If you use a fee based structure, then people are reluctant to pay up front, as their ROI is going to be a over period of 12 months or more, and again ROI is almost completely dependent on the domain's niche and quality.
Another issue with mass development is that if you open doors wide and offer the same service to everyone it's likely that names will overlap and that almost by default induces dupe penalties - ie it would be difficult to create digitalphotoframe.co.uk, digitalpictureframe.co.uk, digitalframe.co.uk and digitalphotographframes.co.uk as 4 completely unique services for 4 different owners without creating an enormous amount of work somewhere in the process, so someone is going to get penalised.
People like Rob Monster at Epik do provide custom development for good sites (only in .com atm though), but he refuses to accept additional sites into a niche where they already have sites built to avoid this type of problem.
It's an interesting area for discussion though.