Hi Firepeet
Well it looks like you have enough space to fit a Blue laser but you might have to move the R/G mount over a bit first to get the dichro mount in. As to parts required, Here's a list as far as I can work out (I may miss something):
Blue Laser module and driver
Mount for laser module
Adjustable dichro mount
Pass Red/Green reflect Blue dichro
Screws/washers/nuts to secure the above to the base plate (glue for the dichro to adjustable mount)
Metal blocks to adjust the mount heights to line up the Blue beam with the Red and Green ones (as required)
Then it's just a case of drilling, mounting and gluing all the new hardware, connecting the Blue laser to the driver output and the driver input to the...Ah! There's the thing!
The CS-500RGY controller that has all the patterns stored on it will be setup to control RGY and if it does have a Blue output socket, it is more than likely disabled. This means you can only have RGB by direct ILDA control and if the ILDA setting on the controller doesn't re-enable the Blue socket, you will have to connect the Blue driver input directly to the ILDA breakout board.
As for analogue laser control, the RG driver is most likely TTL which would mean changing the Red and Green lasers and driver unit for analogue ones (the Blue you buy will be analogue too obviously). The pre-set patterns will have been programed as TTL so again ILDA is the only way you'll get analogue input.
For an easier alternative, you might want to consider an analogue RGB 'brick' module which would do away with the need for any other hardware and only require lining up with the galvo mirror as all the beam alignment is pre-set in the brick. Although I haven't seen any on the likes of ebay (TTL yes), they are likely to be a bit expensive in any case.
Hope that helps.
Cheers
Colin.
Anyone wanting to be a politician, should automatically be excluded from being one!