A counter to the ease of escape that aliens currently have
What if marines were able to research and purchase energy nets - a consumable weapon similar to mines which would cost a reasonable amount of res (10-15), but allow them to effectively lock down the movement of an alien for a short duration by trapping them in a net. I feel the main balance issue in the game at the moment is the speed and ease that aliens can escape, even from a situation where they are completely outnumbered.
With an energy net, a marine would be able to lock down the movement of a lerk/fade/onos for a small duration, enough time for marines to actually kill lone aliens that are invading without backup, and not have situations where one fade can enter a room of 6-7 marines, kill a couple, and blink out with no consequences. There would be risk involved, in case one or more of the marines had nets and were able to lock down your movement for long enough to kill you.
I feel even a 2-3 second duration (reduced by the alien hitting the net) would be more than enough time, and really solve some of the frustration that marines face when trying to actually deal killing blows to the higher evolved aliens.