Hello sir @bagnare ,
Your welcome ! I'm happy to help ... So, what i've done is actually the same as you ! I mean, i damaging a bit the box .. ( Only the top to take it out ).
To put it again on the bike with the box, here is what i've done
... It's not really pretty, but very fonctionnal ! Because, if i want to swap with another battery, it's very sample ! As you can see here on my picture ...
To get lights ? Suuuure ! Very easy .. Get a DC - DC, here is one :
https://www.aliexpress.com/item/1005002 ... web201603_
This one is THE BEST because power is adjustable ! Hope it's gonna help !