So you're asking for the shells to burst after the fuze runs out, regardless of whether they've impacted the target or not?
Say what you will about me being an "off-liner", this will end up being nothing more than a quasi-AA gun for the majority of people. It wouldn't be that hard to create a precise range table for converting range out to 1000m into flight time for each individual gun, thereby creating a fairly accurate AA gun. You could even extrapolate times for ranges beyond 1000m, using data you've collected from the .target command.
Flight time to 2000m is around 2.8 seconds for the KwK 42, in a frictionless enviornment. Now consider that the KwK 42 has one of the highest muzzle velocties in the game, probably for HE shells as well. If you follow that through to its logical conclusion, you see that the majority of tanks will be incapable of utilizing this feature from beyond around 1500m once you include drag on the shell.
Now I don't know about you, but most tankers (myself included) never seemed to have had a problem aiming at and hitting their targets at a measly 1500m range. It seems to me you might want to spend less time thinking of clever ways to make things easier, and more time improving your gunnery.