So was thinking about all the runearms in the game, and their effectiveness. I got to thinking about the lower level ones and what to do with them besides save them for alts.
Here is my suggestion,
Have a runearm that is only crafted by collecting EVERY runearm in the game, I mean every one of em. Take all of em to a melting station, alter, whatever to create this new runearm.
Have this new runearm do prismatic spray or something very similar to symbolize/reflect the essences of the other runearms that were gathered to form this new, crafted runearm. Have every charged rune tier produce an extra spray/effect. So, if only one rune tier is charged it's like a prismatic ray, 2-5 and it's like a prismatic spray. Slap some other good stuff on there like potency and lore, cannith crafting, and ya got a reason to collect every rune arm in the game, even farm for em.
* And if we ever get over saturated in rune arms, at least keep a core group that is collected to make this new, crafted runearm. They could even add to this idea later as more runearms are added, keeping different cores together for melting/crafting, but still keeping the original idea of collecting every rune arm in the game for other conjoined/crated runearms like the original concept.*