Let's think on this for a moment. It is not unlike installing a G1000 into a King Air ...
Seriously, though, to remove the G1000 from a DA40 would be rather interesting from a pure logistics point of view. The G1000 was installed under an STC obtained by Garmin. Removing it ... well, I'm neither an A&P nor a lawyer, so I can't really say.
It seems to me that the issues we see with the G1000 and lack of software and hardware updates are because Garmin got the STC for the G1000 installation in the already-existing DA40 and the interests of Diamond and Garmin subsequently diverged. Garmin found new territories in larger fleets of target markets. This resulted in Diamond's customers being annoyed by an issue that was actually controlled by Garmin. Ironically, this type of surgery would benefit the very company which caused Diamond owners so much ... already.
This said, such an operation would include:
1. Removing the G1000 PFD, MFD, and audio interface from the panel. The resulting panel would have to then be rebuilt as this has to be about 50% of the space on it. Don't forget that the backlighting, circuit breaker panel, and so forth are all built around the G1000 user interface boxes.
2. For those with a KAP140 the hidden turn indicator would have to be moved, too.
3. The engine indicator sensing box (GEA) would have to be replaced as it is G1000-specific. There are kits available, but ...
4. The AHRS and GDC would be replaced with an ADAHRS.
5. The magnetometer may also need to be replaced (out at the end of the wing).
6. The transponder / ADS-B will need to either have a new panel interface or be connected into the G3X / whatever.
7. Then you have the equipment rack under the back. That would be an interesting replacement.
8. The installer would have quite a bit of rewiring and bonding work to do around the airplane.
9. Finally, there are the autopilot servos. These would need to be replaced, though we would still have to find an elevator trim servo.
At the end of the day you would have a new set of boxes with new software functionality. For those who need WAAS, it would be good (and expensive), but for everyone else it would be nice new backgrounds on the maps and maybe a few seconds of time savings for flight plan transfers. There would be no changes in how the airplane flies (though maybe some benefits in W&B or not).
Personally, as annoying as the G1000 software situation is, the system is fine for my needs. Given what I know now, I might have bought a round dial DA40 and upgraded to glass. Perhaps Diamond should start producing non-G1000 airplanes again?