No there is no need for dashcam to access internet, ATM I fill/update data to K1S occasionally using app I made published here. My personal Database contains around 250 Warning Spots of various types from trafic black dot rail crossings/road parts, crossroad cams, speedcams, ... and regarding overlay, if I got things correctly OBD overlay is not inpinted in Video but is shown on DVR Screen, so it is just firmware change issue to also show warining Overlay with SpeedLimits on screen.
For CPL I will confirm when and if DHL release dashcam to me, but usually CPL can be attached to holding ring of cam Last lens with small cut around to make it hold in place better. Housing design needs to be changed a little and it should not increase the cost of original front cam, but 100% sure I would pay extra for CPL as accessory in an instant.
I would also like to publicly thank Rayman for all the support he is giving me regarding jerks in DHL and such support for supporters and future customers is a way to success of an product.