I read more about the different solutions and I came to a conclusion. It seems that the best is to get a DC charger and a power supply. Because most of the higher end chargers are DC chargers. So using an external power supply allows to change to another charger without buying a new power supply. The problem is to find a good power supply at a reasonable price and to carry/stock one more thing.

So probably starting with those is not a bad idea:
- Turnigy Accucel-6 (the 80W is almost the same price as the 50W) https://hobbyking.com/en_us/turnigy-...v-capable.html
- power supply from https://www.ebay.co.uk/itm/AC100-240...-/172227993858 or https://hobbyking.com/en_us/12v-8a-p...y-au-plug.html
The one from hobbyking is only 8A though, limiting the charger.

For people building bots that are (way) bigger, it seems that the Turnigy Reaktor are interesting. And not much more expensive.

BUT at this point I'm lazy. I spent so much time trying to find what is the good choice that I was about to give up building anything. So I'm going to buy the imax B6 AC V2. Because it is A$10 cheaper, it comes with more cables and I don't have to worry about the power supply. It's less powerful, some people have bad experience with it, it doesn't handle LiHV. But at some point I need to buy something and it should be way enough for small batteries that are used in ants.