I can guarantee you that dealing with runners and campers is a very lame experience. Do you know why people in ego-shooters dont like campers ? Exactly. If you get a good position the defender has all the advantages, while the attacker takes all the risks. Thats even more true in a game like Xenonauts where moving up to a position will cost you TU, and in the moment of the encounter you only have 50% of options left. Think about it like a camper camping for 30 seconds, and the first opponent wandering into his zone will be frozen in place for 30 seconds. Thats what it would be. Camping good defensive position and retreating when you are discovered would be the best tactical approach for the aliens, and the worst gameplay experience for the player.
If there is a pacing issue, the map is too big, or the aliens too few.
In X-Division we solve that problem that we divide every map into 3 distinct phases:
1. Fight on the map
2. Fight to get inside the UFO
3. Fight for the command room
That creates a very nice pacing, since the aliens are so aggressive they will sooner or later find you will mean:
1. All aliens on the map will make a fast or slow approach towards you. Which means a firefight until you killed the last alien.
2.Break and safety until you enter the perimeter of the UFO
3. Once you engage the UFO the aliens will defend the UFO while taking maximum advantage of their defensive position (doors, etc ... )
4. Break until the command room and relative safety.
5. Firefight in (into) the command room.
6. End of mission
This creates a nice pace of firefight - break timings, where players mostly know what to expect. One of the core principles in X-Division. This stands in opposition to Xenonauts, where aliens could literally be anywhere and strike anytime. Making the player always having to advance slowly and methodically, which leads to the pacing problem.