Serially driven LCD card with A13

[atys]

I'd like to start a project, and try to get your help, opinion and advice for it.
(Not sure that this is a proper place for this message.)
Currently we use a display-driver card from 4DSystems, called uVGA-II. This is a serially driven small card, the video output is VGA, 800 * 600 pixels, 16 bits / pixels. The card is having an internal character generator. It can handle icon/picture files stored on an SD-card. The main thing from my viewpoint is, that the display is a serial slave, and all the display functionalities are built-up (painted) with parameterized serial commands (and ACK pairs). There are 40 some different serial commands used: writing strings, lines, rectangles, textboxes, icons, etc.  http://old.4dsystems.com.au/downloads/Semiconductors/PICASO-SGC/Docs/PICASO-SGC-COMMANDS-SIS-rev6.pdf
I'd like to replace this uVGA-II (III) display card with a compatible, custom designed A13 board. A13 is the biggest non-BGA (?) processor, so the board design can be a bit more traditional.
The A13 can directly drive an LCD display with the 40 pin LCD (LVDS) lines. That way we can leave out the VGA or HDMI line. The serial line goes to the A13 board. The internal program handles the well-defined serial commands, and can be written in C using DirectFB for graphics.
I hope that driving from SERIAL to 40-pin DIRECT LCD will result a substantial (60 USD) saving. The serial->HDMI and HDMI->40PIN LCD steps left out. LCD-displays with 40-pin driving only is substantially cheaper than HDMI input LCDs.
We used some hundreds of these cards, the device is in production for five years. Now we have to spare every penny from the product. The serial display-driver program is existing, big and sophisticated.
This uVGA->A13 replacement step seems logical for me. I hope it'll be a joy to make. I don't think that there is much demand for a card like this generally, but I hope it can give some years to the life of the product it supports.
First I'd use OLIMEX A13 cards with FLASH for software development. Afterwards I'll make a small card using only the needed parts. (Processor, flash, DRAM, powering, xtal and passives. Cca. 20 EUR component price at Olimex.)

My post/idea didn't generate much response, yet. Here is my further elaboration of the project:
The hardware interface can be more diverse:
1. Asynchronous serial line,
2. I2C bus line
3. SPI bus line
There can be two different application types of the graphic interface:
1. The graphics display is directly manipulated by "serial" commands, as above.
2. The serial line is application data interface. The internal program generates graphical representation based on the perceived state and the events of the environment.
I think that this (ARM based, serially driven) type of graphic interface card is the lowest cost and most versatile method to provide color LCD graphics functionality to simple microcontroller based applications. The narrow serial interface is an extra bonus, the graphics functionality is well isolated from the main functions.
It is interesting, that while using a graphics processor - like e.g. 4DSystems, - is the normal, rational solution one would choose and recommend, (http://www.4dsystems.com.au/) the ARM chip prices are so low, that an ARM based solution can be more economic. Even if you don't use 80% of the pins and built-in functionality of the ARM processor.

What is your opinion about this plan? Did somebody do something similar? Any advice? Potential users?

Best regards,
Csaba / Atys