A +1 to charge rolls that fires once per unit per game would be a modest rule. What makes Elegant Brutes work is that you can make it fire again.
Warp Plunge costs 1 CP at the end of your opponent's Fight phase and places one friendly unengaged Terminator unit into strategic reserves. When that unit comes back, it is set up again, and Eager to Kill turns back on.
That converts the detachment from a one-shot alpha strike into a cycle: arrive, charge with a bonus, kill something, leave before the counter-attack, arrive again somewhere else. It also answers the standard problem with Terminators, which is that once they have won their fight they are stranded eight inches from anywhere useful.
The cost is real. Each cycle spends a command point and a full turn of that unit's presence on the table, and a unit in reserves holds no objectives. This is a Take and Hold detachment, so cycling every squad every turn will lose you the game on points even while it wins you fights. Use it on the squad that has finished its job, not on the squad that is holding the middle.