I have learned to accept every and all file formats and charge a setup fee of $65.00 for every new customer that has provided art, period. I look at it this way, the customer does not need to be burdend with art file setup.
When you buy a piece of embroidered clothing does the shop ask the customer for a digitized file format? No they don't. if you get packaging designed does the box plant demand Flexo / Litho friendly trapped file with a CAD from the customer? NO. So why should we expect to get perfect art files from our customers when we are the professionals using proprietary software.
It is nice to get clean art however the rest of the Graphic Design world does not even think about a blade cutting on vinyl when designing a logo. No matter what small corner of design your in your not going to get the rest of the world to cater to your needs, that's a losing battle.
I do ask for Clean art if that is not available I explain the constraints in terms the customer can understand and use what I am provided with.
I have been able to print a continuous tone image 48" tall from a 2" jpg off the internet by using software such as Genuine Fractals and sharpening or blurring selective color channels.
The customer does not need to know how I did it they just know that every
sign shop told him they can't work with that file. I can! so I got the business.
Derf