I find this to be very useful You want night vision for 9999 seconds? Why not? You just want speed 2 to be on all the time for walking? Why not? You want to jump around like the crazy rabbit you always knew you where? Why not? (For those who don't know with the vanilla command typing the same effect in again with 0 seconds turns it off if you previously set it really high.) People like to use the "just fly more" or "turn up your brightness" but contrary to common belief some people are not in their pitch black basement with monitors that could second as searchlights so they really cant see in dark and sometimes its just nice to walk in your build with a little kick in your step and can also benefit some aspects of building that flying does nothing for. I know you can just drink potions but a problem is they wont work if you try to drink with a block in range of your reach so forget using them in enclosed spaces and they also only last a short set amount of time giving you the inconvenience of always needing a replacement potion in your inventory taking up space from building blocks. I would not suggest this if it wasn't already an option in vanilla so from what I know all it takes is turning on and restricting invisibility as well as use on other players. Give opinions guise.
Meh...everyone is allowed to use brightness and fly mods on the server... Plus you have access to /playertime day...
Brightness mods? elaborate please I have not heard of such things. Flying mods? please elaborate on how this improves walking speed because if it does I am interested (no flying along the ground ≠ walking it doesn't allow for the same movement like getting up/down stairs in a functioning manner). I am very aware of /playertime day but there is a humongous loophole in that logic, you cant make it daytime in a cave. believe me I've tried.
Search on google "voxelmodpack." It has almost everything you're asking for. It's a mod pack and there is also an installer for it. I'm on my phone right now so I can't get you the direct link to it. It's made by the voxel box
Quiet is right, there is no need for /effect when you can just use /playertime day and fly to places instead of walking. Also you don't walk around as much in a creative world. At least I don't.
QuietSea has put some good points in but /playertime day is not one of them. you can't make it daytime underground. the only time brightness ever becomes an issue is underground anyway because moon light is bright enough 80% of the time above ground. /playertime day is irrelevant to brightness problems.