It's complicated. One of the complications is requiring anything. Most trade agreements now in place defer major standards compliance in aviation to ICAO, and ICAO ends up being lowest common denominator when it comes to rules. Simply, less rich countries don't want to pay for every possible feature.
Another complication is there's almost no such thing as a "backport" in aviation. The equipment a particular plane model is certified for is the equipment it has for life, save for some software updates. And this isn't in the category of a software update, it's new physical equipment. The easiest part is a new weight and balance for every airplane getting the new equipment. Harder is wiring the thing in, and getting it space in the cockpit - that's often quite difficult. If it requires integration of any sort, very difficult. There's extremely low willingness to substantially alter certified aircraft. There are individual systems that make up a whole, change any one part, you change the whole. The liability is too high for the return, these kinds of lost plane events are rare.
Actually, your mistaken. Cockpit avionics upgrades are relatively common, even in small aircraft like Cessna 172s. Considering a new Cessna 172 is around $250k, and a refurbished aircraft, with new glass cockpit is around $50k (and sometimes significantly less).
Aircraft have whats known as a Supplementary Type Certificate, which permits changes to a certified aircraft. Even a major upgrade from radial engine to turboprop has been authorized for some aircraft, including DC-3 transports made in the 1940s.
Another example is Southwest Airlines. The 737-300 series jets have glass cockpit upgrades for a common configuration between a 737-300 (Classic) and a newer 737-700 (NG).
If the ICAO mandates upgrades, it will happen. It might not be cheap, but its quite doable.
I wonder if the cost to Malaysia and Malaysia air at ~250 per month would have been more than all the monies they've had to pay for this two year long search :-/
I was thinking about this on a motorcycle trip to Alaska. For $250 one can buy a consumer device that updates my location via satellite every few minutes to display on a web page. $35/month, and they have cheaper plans. Were I to have been eaten by a bear, or splattered by a semi on the Dalton Highway, my wife would have at least known where to recover the body.
Any yahoo with $250 and a shipping address can have one of these, yet two years later we still don't know where this Malaysian flight went to?
This is exactly what Immersat are now offering. Almost all wide-bodied jets already have the senders, and Immersat will stop charging for it, so everyone will hopefully start enabling it.
Basically why can't we use the Inmarsat network for more than distress but any and all planes report to some tamper proof system every minute?
(Yes I know how many flights there are, but you don't need to store the data once a plane has reached its destination successfully)