Nightvision is currently the only equipment which explicitely requires batteries to be used (since PFR isn't available that early): Shields totally work without batteries, they just aren't as effective because they can't recharge as fast. Discharge defense has enough charge for 1 or two shots, which is quite decent already. PLD works, it just doesn't shoot as frequently without constant power supply. Personal roboports have enough charge to recharge about 23 robots which is plenty for small works. Exoskeleton requires constant power supply anyways so batteries don't even help.
Only nightvision absolutely requires a battery to work and only nightvision is available so early that you would actually like to not need that battery.
Nighttime is very restrictive, basically preventing you from doing any serious work, unless you play in the dark and increase your screen brightness to gain fake-nightvision (I think many players do that, which is a bit sad). Lights just don't really help, since their radius is so small that you would require unholy amounts of them to get anything done and nightvision is obviously meant to be the solution to nighttime.
To make lights usefull, their radius would need to be at least doubled, better tripled. Then one could also reasonably make nightvision a bit harder to get, since one has a functional early alternative.
Also, from an aesthetic point of view, I would like lights to be split into two items: a "signal" which may work as currently, and a "lantern" which would be the primary tool of large-scale illumination (with a different sprite, might actually fit well into the theme of factorio).
Another aesthetic point is the fall-off of the light-radius: I think it would look better if light sources (all of them) would not have a certain radius with full brightness and then a sharp drop-off into nothing, but instead fall off smoothly over their entire radius. Then one could also increase the light radius of all sources (lanterns would still need a much larger area on top of this), giving more total coverage, just with lower light levels away from the sources (but still better than nothing).
Ok, now I'm just spinning off my mind and I don't know inhowfar this is worth implementing: One could make light levels of light sources add up in overlapping areas (might need an upper limit). One could make adjacent light sources increase each others radius, similar to how using several personal roboports increases the working area (since their light adds up and is therefore enough to illuminate further areas).
Nightvision could be restricted to a certain area around the player (again with a smooth fall-off), drastically improving vision, but not giving the full-screen vision of daytime and therefore not making lights completely obsolete. In this case it might be worth to implement "mark2 lanterns" (may want to call them "floodlights") with a serious light radius for late-game illumination.
Nightvision could get a mark2 version including any of the following features: larger vision radius, lower energy consumption, smaller grid size (1x1 would nicely complement belt immunity), better vision (brighter, less graying, better fade-in/-out at dusk and dawn, one could worsen vision quality of the mark1 version to make this more notable).
I am aware that one could simply make a mod do this, but as I see it, mods should provide additional/changed content, not fix issues of the base game. So one would need to determine whether the current light system is bad and requires fixing, or if it's fine and changes are the domain of modders. I tend towards the former, since my current philosphy is: "use bright screen for fake-nightvision, get real nightvision ASAP, never think about it again", which can kind of be reformulated into "fuck this problem".