for actual time, the community knowledge is very limited on how to custom build sensors and weapons, all that is behind SDK.
we could build simple custom systems, but always FC3 is needed in some way, because it's the only system we can inherit without DCS Dll (SDK)
the MAP and Terrain Radar are real time, I think there is a Simple MFD since years to show that concept, that mater is how to use them to get targets or SPI on them, because of the said reason.
Also to build multi role / multi crew capability, not possible when using FC3 avionics, that's why people do add multiple variant of the aircraft Grippen for example.