Gregg, hello.
Thanks for the info. I'm not sure 5' by 5' would work...I would have to see the image of what you would like done. If the image works for an exact square, we could go with it, but, usually, this is not the case. A more rectangular canvas might work better.
I also need to see the image to know if watercolors would work over the oils, especially at that size. You won;t find too many watercolor portraits at that size because the intensity of watercolors, at that size, does not match the intensity and richness you can get out of oils -- and with the way I use my knife, a portrait at that size would EXPLODE off the canvas, I can promise you that.
The price for something that size would not be cheap, no less than a few thousand dollars, probably even more. I can know from looking at the image. My 42 x70 INCH oil/knife portrait canvases sale for between 5K and 10K..
Let me know.
Always Believe,
Warrior