OK, let's clear this up. Sorry to contradict you Causidicus, but your info is unfortunately incorrect.
I am 100% certain about the following having spoken with the guys at Campagnolo in Italy.
1) You definitely need a V2 charger. This is nothing to do with anything as sophisticated as charging indication. The voltage is the same, yes, but it is as simple as the fact that the connector is different. Since the connector is at the end of a fixed cable that comes from the main 'box' of the charger, it is not replaceable. Therefore, you need a V2 charger. It is like when Apple changed the connector between the iPhone 4 and 5 (except you can't buy an adapter for a few cents off eBay - you need to spend $100 on a new charger). Grrrr!
2) You don't necessarily need a V2 interface unit, but you might want to buy one for 2 reasons. Other than these 2 reasons, it will function perfectly well. Firstly, since the diagnostics will no longer be housed in the battery because it is hidden in the frame, the diagnostic LEDs are now housed in the V2 interface. You can therefore either forgo the onboard diagnostics and not buy a V2 interface, or you can benefit from the onboard diagnostics and buy a V2 interface. Diagnostics will still be available by plugging a computer into the V2 battery, it is just that the battery itself won't have the LEDs. The V2 power connector also has a data stream, not just power. In reality, the V1 diagnostics simply showed where in the system the problem was, not specifically what the problem was, or how to fix it. Its use was therefore limited anyway. Secondly, to benefit from the new software changes you need the V2 interface unit. There have been some problems with the early front mechs losing their memory and over shifting and the distance by which the rear mech over shifts slightly to shift gear is variable in V2 depending on which cog you are in at the back which the firmware fixes solve. You cannot simply update the software on the V1 interface (as I pointed out in a previous post, this is one of the areas where V2 EPS lags behind V2 Di2). If you haven't experienced problems, you might not want to bother. I personally have not, and for what a new interface will cost, I am at least going to try not replacing it at first.
3) There are only 2 ways to charge the internal battery. Firstly to run the charging extension cable up the seat tube and remove your seatpost every time you want to charge and fish the cable out. Secondly to either buy a frame with the third hole pre-drilled (curently only Pinarello), or drill a third hole yourself. Contrary to what you might have seen, and contrary to what would have been a great solution, the charger port is not the second bottle boss. It is categorically a third hole. Campagnolo recently uploaded the technical videos to youtube. Watch these for absolute confirmation. Also, look at the battery. It has 4 cables coming from the bottom. 1 - to the interface. 2 - to the front mech. 3 - to the rear mech. 4 - the power cable. It would be impossible since the battery is flush against the inside of the seattube inside to run this cable through the same hole as one of the bottle bosses.
4) With regards to the charging status, the V1 interface will still show the charging status through a series of green and red LEDs using the existing functionality, just as it currently does. Also, since the trigger to stop charging is housed in the charger itself, there will be no loss of function by not buying a V2 interface.