.... how much choice does your airline get in the avioincs fit for your aircraft
Hugel, I hope this isn't granny and eggs but are you familiar with civil ARINC standards? Brilliant idea from the 40s. Aircraft in production are wired and racked to a certain Standard. Avionics manufacturers produce boxes to fit the Standard wiring (pin outs) and racking. Airline customers can then go to several manufacturers to select their avionics boxes/systems. Keeps the whole thing very competitive and eliminates 'single source'.
There are three classes of ARINC Standards:
ARINC Characteristics: Define the form, fit, function, and interfaces of avionics, cabin systems, and aircraft networks
ARINC Specifications: Define the physical packaging or mounting of avionics and cabin equipment; communication, networking and data security standards; or a high-level computer language
ARINC Reports: Provide guidelines or general information found by the aviation industry to be preferred practices, often related to avionics maintenance and flight simulator engineering and maintenance