I would pay for some well crafted mission packs. Maybe have some missions that span multiple reserves to complete. Just some well crafted and interesting story lines .... Also think about including a useful reward for completing the Story Arc ... Like a new weapon, a new cosmetic or even an opportunity to take down a unique trophy animal....
Make this part of a new way to get a G1 other than grinding ..... Maybe not get a G1 thru completion but a greater chance that you will spawn a G1 and you have to then hunt for it to find it ...... explained more here #1089958791103119502 message
People would buy the DLC and complete the missions just for the increased chance to spawn a G1 ....