Consideration of dimensions of input art work and the likly dpi required in the final image and the available resolution of current cameras it seems that an A3 scanner with 600 dpi or better resolution would be a superior solution to using a camera in this application.

---

A recent stack exchange question discussed requisite scanning and print resolutions for various applications. I'd guesstimate that 100 dpi would be on the low side of what you'd want, that 200 dpi would probably be adequate and 300 dpi very good.

To achieve a ~= 40" x 30" print at even 200 dpi you will need a 40 x 30 x 200^2 = 48 megapixel image. If you are intending to acquire this in a single photograph then no 35mm camera available has enough resolution.

At 100 dpi you need about 12 mp and suddenly most DSLR's and a number of prosumer cameras have notionally high enough resolution. A good 12mp plus prosumer camera with non removable lens and lots of light would nominally meet this requirement, but you are at the lower end of the specification.

The 16 x 12 image is about 2.5 x smaller linearly than the output print so to achieve an output resolution of 100 dpi you'd need a 250 dpi minimum scan and for 200 dpi out you'd need a 500 dpi+ scan. If you want 300 dpi in the final image - which would be liable to be the upper limit of what you'd want - you'd need around 900 dpi from the scanner.

16 x 12 is larger than A4's 10" x 8" so you'd want an A3 scanner or at least one comfortably larger than A4. Good quality A3 scanners with X and Y direction scan resolutions are available. Fully professional versions sell for thousands of dollars but an eg Brother MFCJ6510DW A3 Multifunction Printer is under $300 and MAY suffice.