Unfortunately I can confirm that you will need a new charger for the new battery.
Not when you check the voltage outputs of the chargers. They are identical. No new charger required. No new DTI required, either.
...drilling another hole in your frame (seriously, who is going to do that when it might be redundant in a year's time?), or having to remove the seatpost every time you want to charge the battery is not well thought through.
Not required. Look at the technical documents available online. Charging is through the bidon mount. No new hole required.
Yes, there are no change to the charger. Same as before.Edit:it was confirmed that there is a new charger for the new battery
The old interface is not compatible with the new battery because the new battery has no led to show the state of charge since it was designed to be installed internally. That feature is now on the new v2 interface. You can use the new v2 interface with the older battery though.Edit:I had the charging and diagnostics mixed up. If you use the new battery with the old interface you won`t be able to use the new software and diagnostics.