Designing a standalone master DMX Controller

I'm actually looking for a low cost standalone DMX master controller (with internal memory to output sequence without using a PC) after looking through some of these products they are really expensive for me.

So now I am thinking of building one. How feasible would this be? Please suggest. I have got some background with PCB design, 2 layer circuit is not a big problem I would say.

I am actually helping my brother with his led signboard business. I will be using this standalone dmx controller to output high current PWM signal using a DMX Decoder like this: http://www.alibaba.com/product-gs/453143512/LT_880_24CH_DMX_decoder.html