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I just thought of how they could make me want to take them/ update markerlights. Fluff wise they could say that markerlight technology has advanced.
If a squad hasn't moved this round every hit a firewarrior successfully scores on a unit places a markerlight. This allows another unit to fire at it as though it were twinlinked. If the weapon being fired is already twin linked than it will increase the ballistic skill by 1. A unit may not receive both benefits in the same shooting round. Ie you can't spend 1 marker to twin link then another to up the bs.
12 firewarriors shoot.6 hit you now have 6 lights.1 unit of fireknives shoot they count their weapons as twin linked. A unit of deathrains shoot they get +1 bs. To make it so seeker missile spam isn't overwhelming require 3 lights to lock on and be spent for a shot. Give seekers the option of being fired like missile launchers. Now firewarriors have a "heavy weapons option". You can make this upgrade cost points like a heavy weapon would.
Thoughts, questions, opinions
I actually see Firewarriors getting their own sort of buff in the hull point rumor. If Firewarriors can glance vehicles to death easier now then I wouldn't be opposed to using the sensor towers on a full squad of firewarriors.
And I like your idea, however I use markerlights to remove cover while making my suits accurate on their own. Twinlinked missile pods and BS4 HQ fireknife squads always do right by me.
I also use it to remove cover. I don't think Gw will give us that again however. When the ability was initially was given the game was at a point when cover wasnt so prevalent. Now that cover is such an instrumental part of the game I don't foresee us getting that aspect again.
On the other hand cover is supposed to be getting downplayed in 6. I only played in 5th so I can't say that I notice how abusive cover is.