-Soulstones should not be introduced at lower levels. This is because Soulstone are endgame content and can only be farmed through endgame content. However, I do see what you are trying to say is "find a way to make it happen," but that would contradict the nature of the level lower level dungeons since all monsters are elementless and should remain that way. Introducing an "Element" mode in those dungeon *might* fix it; however, as you can tell chances are it will be more difficult than the current manic. I don't think they should introduce this as a reward in the leveling box either at lower levels. However, it would be a good idea to introduce this at lv 55. I heard the new KR box gives Aurith gear, so they might as well provide the soulstones lv 1 with it.
-Buffing manic xp will not change anything much. Why? Simply because players don't go back after they have completed their quest. It is simply not necessary. For us, people who already capped, might be helpful since we know and have this and that, but for them is a different perspective and experience. Chances are they will only try manic once, then give up after experiencing the difficulty. It is also important to take time and number of times the player die into account. Manic might be buffed, but if the time it takes to complete is three times higher, what would be the difference in xp for that amount of time? If anything, you will only be saving Energy. We can't also forget that unlike before, there are not many people leveling for obvious reasons, so "parties" should be out of the question. Afterall, leveling is not a content, it is a phase to a content.
-Regarding other information about not teaching players about brooches and whatnot, I'm not sure how would they address this? If anything they already tried to addressed it. The leveling box already give brooches they can try and upgrading materials. There are also side-quest that addresses upgrading. It feels like you want them to "forcibly teach" them how to do any of this when is already there. From all honesty, all this information stuff is supposed to be passed down through Guilds and whatnot. I have never seen a game that have addressed these "issues." Information is always passed down through players who already know this stuff.
-I'd like to say I'd agree with your point about Akanshas, "giving specific akanshas to players" that are necessary. MK2 for stamina, etc. Of course, you don't want to give away card of too much value or tons. If anything it'd be like this:
Rocco: Active card
Candus: Shade / Luke II(the miss rate is evident while leveling), passive
Grace: MK2,, passive
Ruin: Another active card/passive
*However, if this will be considered, then it should be addressed with the upcoming akansha revamp
To end this, I would like to say that buffing manic xp will most likely only benefit those who are capped. Considering what I've stated before, implementing SS at lower lower appears to be difficult and the other stuff have already been addressed in one way or another.
Personally, I don't think you should expose new players to manic considering the lack of players leveling up. It is safer to assume that the upcoming players will have to solo everything all the way to lv 55.