Working on your idee Drazen I come up with this my self. The idee of having the housing on top of the roof peaks. I like that, removes the problem with the water that runs down the channels.
Simpel concept, box in a box. The outer shel (the blue one) that has the solarpanel works as waterproofing for the green box that house the batteries and maybe the small circuits that runs the leds.
The cut outs for the screws onto the roof on the green box is there so you can fit it to all roofs. You dont need a specific distans between peaks.
All you need is 6 screw, 6 nuts and maybe 4 washers.
The green house can easly be modifid to fit more bateries and or more electronics. If you need more or longer power to run the led.
The cables can run throuh the small cut outs on the green box and under the ledge of the blue box. To be connected to the bottle.
*Update with two small renders.
Made a small cut out under the solarpanel for some wires, this grove can go the entire length of the blue box if needed.
Also showing the cabels going through the green box and coming out the other side for connection to the bottle/leds.
Btw the last rendering is something that is not within the file. If you want it with the groove, just ask and I will upload it.
This is more just to have a place to put up idees...