The operative phrase here is “….indistinguishable from Toyo film holders….” I think there is a great market for a high quality 5x7 holder. In 4x5 abd 8x10, there is a quality difference between the Toyo holders and the Fidelity/Lisco holders currently sold. For me, the higher quality Toyo holders justify the higher price.
Toyo no longer makes a 5x7 holder. So the talk on the LFF about getting Toyo to make another batch of 5x7 holders has my serious interest. And over 40 other photographers have expressed serious interest on the LFF for a 5x7 Toyo holder as well.
But again, the operative word is “indistinguishable”, where quality is concerned.
The stainless steel slide would be a nice touch. And have you considered the very popular 7x17 holder?