Sorry, but I don't think I understood you correctly, so I will try and address your points in detail.
GPA/GPR support for a 2nd PDM - Not currently planned.
GPA/GPR support for C125 (or other devices) - Already supported. The C125 has M1 receive CAN template in the software. In the GPA/GPR package you can select CAN as an input for most non-critical sensors and switches.
GPA/GPR RS232 GPS - Already supported, just Set the 'GPS Interface' parameter to RS232 Port (obviously this only works with M150 or M190 as M130 and M170 do not have RS232 input.
GPA/GPR light bar support - The SLM is already supported, just go to 'All Calibrate' worksheet to set it up.
GPA/GPR direct wired lambda - Not supported (see point 3) but LTC lambda supported for individual cylinders, banks and collector.
Yes, you can add workbooks and worksheets, either to the packages or to your PC based workspace. Just go to the Layout menu and then select Layout Editor. You will need to unlock the package workspace before you can add to it, to do this click on the package name ('GPR (M150)' for example) then the Unlock button. This is all done via M1 Tune, it has nothing to do with the M1 Build software.
The M1 ECUs do not support direct wired wideband lambda, you have to use an LTC for this purpose. The M1 can support narrow band lambda sensors, but not with the GPA/GPR packages.
I am not sure why you need the windows file extensions as all file handling should be done from within M1 Tune using the proprietary M1 zip format, not via Windows Explorer. If you wish to send a package to someone then you should right click on it and select 'Export File...', then send this *.m1pkg file to the recipient. They will then double click the zip file which will extract the package to the correct folder. All packages have to be in the Package folder in My Documents, you cannot move them into other folders or even sub-folders as M1 Tune will not be able to see them.
There are no tyre pressure or temperature monitoring features in the GPA and GPR packages.
MoTeC Europe Ltd