These are a couple of variants that we have thought of which you can try in your games.
Instead of the normal setup, take all the Location Cards (both basic and special) and shuffle them together. This will be the Location Deck from which you will draw.
Take the bottom 20 cards from that Deck (without looking at them) and set them aside. These will play the role of the unused Special Locations.
This speeds up the setup process, but it makes the game less predictable since nobody will know how many copies of each Basic Location Card will appear.
Limited Space Variant
Normally, you have unlimited room to build your Space Station. So if you realize that you cannot physically place a card (for example because your station has reached the edge of the table), you just shift all of your cards and move your Station so the new location fits.
With this variant, you are not allowed to do so - you are limited by the surface on which you play. If the side of a location card is near the edge of a table, then you can't play a location next to it.
Moreover, if the locations built from one player get near another player's Station, neither player can expand in that direction. To maximize this variant's effect, just choose a smaller playing surface than usual!
In order to play the Aggressive Mode you will need a Conflict Set. Within the basic game you will find the Dispute Conflict Set and more sets can be found in expansions. After you've chosen the Conflict Set to play with, set aside its 12 cards.
Play the 1st round the same as in the Non-Aggressive Mode. Then, before drawing any cards for the 2nd round, shuffle as many Conflict Cards as 3 times the number of players into the Location Deck (e.g. 9 in a 3-player game, randomly chosen; all 12 in a 4-player game).
For each of the next 3 rounds, each player will draw an extra card from the Location Deck (for a total of 7 cards per player). The turns are carried out the same way as in the Non-Aggressive Mode with one exception: When a player selects a Conflict Card, he cannot "build it" since it is not a Location Card.
Instead, he applies its effect by paying the cost on the Conflict Card (in the case of the Dispute set, that cost is 1 credit). The other two actions can be taken as normal.