I'm curious as to the mention of a "Web Control" and how long we have to wait until we can use DirectX for graphics, seeing as I've been trying to use Pis for digital signage[1] for a while with varying results (we've since started using cheap Android boxes with great results, but I wish I had more choices).
I had to recently roll my own signage solution and have built something I think is pretty compelling using Yocto[1]. I'm using CuBox-i devices running Linux and Midori (which is based on WebKit). I don't know if it does accelerated rendering but the boxes are much more powerful than Pis (and are a lot less dev-kit-y than Pis). If nothing else, hopefully a pointer to Yocto will be useful to you - it's pretty great.
Thanks, I'll look into it. Right now the Android boxes we're using cost €50 (less if you buy in bulk) and do both accelerated rendering and HLS video, but I'm always looking out for more options.
[1]: https://github.com/sapo/digital-signage-client