I generally play in a party of 3 (including me). That is mainly determined because that is the number of people I know who also want the play the game multiplayer.
Includding the player, for default the party size could be 4, for something more hardcore, could increase to 6. But would be good if server owners could change how many players may have in a party, but that would require a compact party interface for that, in case have many party members in a party.
I have an idea for parties instead of inviting someone using their name how about a panel would appear and it would show all the current players online on that server and you can check a little box between their name and it would send them an invite,
I think it's safe to assume that average party size is somewhere between 2-4; but potentially up to 8. Honestly, if we are to see large group-like factions. Multiplayer needs to be a bit more expansive and unforgiving in a term of PVP where the bigger the group, the better the resources and control of your solar system.
I usually play with 2 to 5 persons (so typically the party has 6 members). Oh and because this isn't spammed yet I hope you read this tiy, it's a small please: Start promoting the game more for people with 12+ because all my friends laugh me out when I play starbound becuase "I play child games", I like how starbound plays but add those few blood pixels with different color on each planet. That schould make people shut up with the whole "this game is for children for which terraria's cthulus eye was too bloody and brutal". It really sucks... really...
How many players does Starbound currently support? While I, unfortunately, haven't tried multiplayer yet I think that when the day comes for me to play Starbound with my friends at a LAN party the ideal party size will be 6-8 players.
I normally play with 5-6 people. I think in addition to working with the party HUD, a couple symbol features could be added too. Maybe you could mark a player with a Star (for example), and that star will appear over the planet and solar system that player is on.
I've played with larger groups and it sucks unless we're on different planets. I enjoy it more when there's about 5.
If I'm not playing alone I typically play with 3 and sometimes just 2. I didn't think the HUD was really all that bad all things considered. Any ideas on what you're actually looking to change, @Tiy ?
After giving this topic much thought I have come to the conclusion that the optimal party is composed of no more than one player.
I'd recommend a togglable resizable party menu in which you can drag and drop player names in custom priority. Being able to scroll through if you have 7+ would make this work.