I would pull a new cable + and - with a fuse near the battery.
Really..?
Is that because there's no suitable point within the car, or for some other reason?
I agree that you should put a new cable in to link it to the battery. Yes there is a reason. Modern complex electronics have many computer all with memories, and the drain on the battery can get quite noticeable. On-board computers these days often monitor electrical outputs and trip out some things after twenty minutes, and if the car is not used for a while (say 72 hours) then they shut down more or go into standby modes. This is all to save your battery when the car is left for say three weeks whilst on holiday, so it should start when you get back.
So a) I doubt you'd find a suitable place, and b) you would need to make sure it wasn't something that got cut-off after a period of time anyway.
Roy