I have been thinking for a while and recently started to make some drawings for a new mechanical design. To keep the cost down I will try a laser-cut assembly from acrylic and some 3D-printed parts. I will also try to use a belt for the slower moving Y-axis (one microstep per pixel row) but I am unsure if this is unwise as stepper motors are somewhat unprecise when moving one microstep at a time. Since there is a potentially dangerous laser involved I will also add a lid to the enclosure, with interlock, to ensure that it cannot be operated when open. 

My original design is based on a GT2-belt and a 17T pulley for X-axis movement, this results in a near 1200 DPI resolultion when switching the laser in a 1:1 relationship between pixels and motor-steps (@ 8x microstepping). For now I will keep this as it simplifies coding and a humble MSP430G2553 (USD 1) microcontroller is up to the task of driving it.

I will soon add a new project to my GitHub account for this project, this far I have made an Inkscape drawing of the acrylic parts, and a FreeCAD drawing of the laser head assembly (to be 3D-printed). These are very much work in progress and can NOT be used for production. For the electronics I am working on a new laser diode driver PCB, this can be used with a MSP430G2 Launchpad or a custom controller board.

The original firmware is updated so it can be imported directly into TI's cloud based development platform.