You mean like these?
Massive Endeavors (Wonders)
It would really spice things up to have some Wonder building goals along these lines. Some of these wonders might take a long time to destroy or you can assault them with ground troops and destroy the structure more quickly that way. (act at the very least as a mineral sink, I am often looking for other things to use my minerals on other than more Battleships)
Cruise Ships - Build the largest cruise ship, move it somewhere and it adds 10% happiness which reduces by 1% a month. Every time someone builds it, it gets bigger and costs more. Only the biggest cruise ship can gain the bonus. Can set them to "explore" where they will just jump around every colonized planet.
The Great Galactic Zoo - can only be built after certain anomalies have been completed and a few techs have been researched. The Zoo grants a +5% happiness bonus to the empire that builds it and a +2% happiness bonus to any empire that maintains open borders. Could be tied to new anomalies, the more anomalies your science ships find towards this the better and greater your Zoo compared to everyone else.
The Lunar Bridge - build a giant bridge from a planets surface to one of its moons housing the largest shopping mall in the Galaxy! Increase energy credits by 5% for the nation that builds it and 2% for any other nation that maintains open borders with the building empire.
The Galactic House of Unity - Build a massive space station which creates neutral space for a short distance around it. It acts as a wormhole hub to all other capitals that have open borders with the building nation. All nations can use this as a wormhole hub provided they have open borders with the building nation.
The Grand Galactic Games - everyone puts in a bid if they so desire. Energy = 1, Minerals = .25, Strategic resources = 100 (10 years). The winning bid holds the "Games". The host must build a Great Galactic Games building on time which is an expensive building but gives +5% Happiness permanently for the system. The moment the games start ALL wars with this nation are ended in a neutral white peace and nations are prevented from declaring war on the host for 10 years. The host gains +20 trust with all other nations.
The Halls of Dynamic Thinking - The great minds of the galaxy are attracted to the planet with the greatest library of knowledge. Grow and upgrade this building tile so that it dominates the planet. When a tile reaches level 5 you can expand it into another tile until it covers the entire planet. The owner of most upgraded Hall in the galaxy gains +1 research slot to work with a scientist.
Custom Built Planet - Sentient races need not dwell on natural planets when one can be created from scratch. Requires an enormous number of Terra-forming strategic resources, one use freighters that are sent to the system where the planet is being built. The planet grows - one tile at a time. The Empire with the largest planet gains a superiority bonus. Their core species gains +5% happiness.
The Galactic Grand Prix - Make a ship, add it to the event and watch it compete with the other entries, is it a good idea to just have the fastest engines and optimum power? Resources can be added to your vessel, minerals, energy, strategic resources, leaders, the more added tends to make a faster ship although a certain level of randomness is abound. The race path may lead through several system inhabited by space creatures or worse! The winning nation has a +5% sub light speed boost for 5 years until the next event. They also take the prize energy and gain a trust boost with all nations.
Stellar Citadel Defence Grid - A system spanning mix of defence stations, gun platforms, automated defence drones, path blocking monoliths, hidden crossfire kill zones, sensor jammers and mine systems. All interlinked in a mesh like structure supported by a wave of automated repair tugs. The defence system grows to cover the entire system the more you invest. The largest defence system gains the owner a threat, trade research bonus.
Factorium Al Dente - A tile dedicated to the making of fine manufique delicacies from all living things. The higher its level the more influence it generates for every purged pop in the nation.