Online Text/Lettering Designing Font Tool with checkout.

Looking for developer for making phone responsive or phone friendly online text/lettering designing tool with checkout for my upcoming web store. Tool design should be very simple, like in picture attached, and tool functionality has to be like in picture attached. Actually tool in picture is some existing tool print screen with my add ons in red color. All additional info like area calculation formulas and currency exchange rates, font and color choices should be easy changeable by me. Most important thing is that this tool should work properly on iOS and Android devices. And this tool should export result after checkout is made in SVG or PNG file format. As my experience shows most challenging part is to create engine which could properly show text or lettering LENGTH and HEIGHT accordingly to each font proportion , and how text looks when custom sizes are being selected. This is not an urgent project, but it will be great if I could launch this tool in January of 2018. Please feel free to contact me if You have any questions. -- looking forward your propositions, Laura