Leveling Up Earlier Era Characters That You Missed

I recently returned to the game and missed the opportunity to level up the first two characters in this era. I know as part of the requirements for Rotta the Hutt you need R5-D4 at level 95 and all of the marquee units at 4 stars. There is still a way to get the earlier marquee units to 4 stars via crystals but there doesn't seem a way to get enough of the MK1 ability modules and MK1 performance cores via crystals. There also isn't a way to get more of the MK2 currencies in the store even at all. I feel like there should be some way for returning/new players to reasonably get the earlier characters up to all the requirements for at least the tier 1 of Rotta the Hutt.

Even if I wanted to spend money or crystals on the earlier era character shards (R5 and Zeb) there doesn't seem like there would be enough of the era currency for me to even level them up. It feels like it is impossible to catch up within the era if you join even one or two characters too late.