I'm basically going through the same thing as you at the moment, and what I'm trying to do is add things that fit all my friends playstyles.
First decide if you intend running short or long games. If these sessions are meant to be "start, play a while then not play that same game again", then big modpacks are a bad idea, because they extend the time it takes to basically get to the same tech in a regular game. A decent in-between expansion mod is the single file AnonyMod, as it adds extra ores and tech and will force larger bases and more complex setups without adding a tons of files. That Mod alone will force some convoluted setups.
You can then decide if your game is mainly base building or an excuse to kill biters, and say, use SpaceBook to space out players in their own areas, so you can join up bases and share resources, or add a couple of "enemy" type mods to create a survival type game, say RampantAI, Swarm, Bob'S Enemies etc etc, forcing you to actually concentrate on better defenses while expanding.
If your play sessions are random and sporadic, I would basically just go on the Factorio Mod site and do some random browsing, then just download whatever grabs your attention (I also grab a screenshot of the explanations page as a jpg) and dump them all in a collection folder, then every time you want to start a new game, you can just pick a handful that you like on the day, and give a unique play-through for that day/week. Your friends will get a message your game needs mods and they can just download them from the game. I already told my friends to install a separate copy of Factorio (as they all have Steam versions) so they dont have to constantly disable/enable a bunch of things.
I'm currently doing mod stability testing for a long-ish campaign type game I want to run on a map of earth, and these are the ones I have (gradually) added up to now, still looking at a few more, I'm giving the list and explanation to show that if you add something, there really should be a reason as to why you do so.
Additional-Turret_0.1.4.zip - Give players more combat options, Maybe even too many
* These two together allow an admin to add things dynamically to the map if needed, even say an "enemy base" with turrets that will shoot at players. I my game I repopulated an area of Biters while my players were offline
and you can also change the default values of how how long it takes for new biter bases to be created, if players are having it too easy.
creative-mode_0.2.8.zip
SpaceBook_1.0.26.zip
* The default enemy behavior is more annoyance then a danger, so these two up the threat a bit. An MK2 suit with full gear and a flamethrower still wrecks everything.
Rampant_0.14.10.zip
Swarm_1.0.6.zip
* Quality of life mods really
Laser_Beam_Turrets_0.1.8.zip - looks good
long-reach-research_0.2.1.zip - players getting annoyed with limited reach.
PavementDriveAssist_2.0.3.zip - This now conflicts Teleportation (installed later), but the original idea was to speed up getting around
research-queue_1.4.3.zip - so people don't just interrupt things all the time
Single-Splitter_0.0.10.zip - we were getting tired of the standard "splitter and curvy bits" kludge, and this makes cleaner bases.
beltSorter_0.3.5.zip - also added for cleaner looking bases, but, it's bit OP actually
might tweak costs and research
StickyNotes_2.1.3.zip - tell people what the hell you are doing on the map
Enhanced_Map_Colors_1.3.9.zip - helps figure out other people setups
Factorissimo2_2.0.2.zip - just because its a fun idea
gravestones_1.4.17.zip - added because only getting killed by lag and losing everything sucks
KBlueprints_1.14.1.zip - share BP's with mates is awesome
Teleportation_0.14.9.zip - As I intend to have bases around the world, walking is just inconvinient.
TruePeacefulMode_0.0.1.zip - Allows players to decide to some extent when things become nasty.
Warehousing_0.0.11.zip - with lots of players, "just Chests" become annoying rather fast.
bullet-trails_0.1.2.zip - visibility tweak.
AsphaltRoads_1.0.2.zip - make nice looking bases
Bottleneck_0.6.2.zip - Very useful when you have to deal with other people spaghetti setups.
robotarmy_0.2.3.zip - Currently just for testing. Unsure if it will make it to campaign.
Hope this helps.