Talking [Q] single rom for multiple devices

guys i was thinking recently that all apps in android are modular i.e. they manage to fit themselves in any phone of different resolution or configuration,the same version of a particular app runs fine even on a low budget phone as well as a high end phone and sometimes even on tablet.the roms are comprised of many such apps ,android is modular and everything even lockscreen and settings are apps.

My point is if a single rom can be made which will be compatible with maximum number of mobiles . i do realise that there may be a few problems with wifi, bluetooth and maybe camera .but the first step is to get the rom booting.and of course kernels will have to be different for different devices,and maybe the problems with wifi can be solved by flashing kernel specific modules.

if this concept is feasible then the effort of porting roms and uploading them will be negligible .

if you think that this concept is new and innovative please reply and hit the thanks button