Idea 1 seems somewhat pointless to me. A 5% fluctuation seems like it barely would impact the situation. But I like the idea of larger rates of fluctuations, and perhaps rotate prices around or among 2-3 destinations. It would be cool to see weekly market updates on changing prices. Jump them around, even to random places for random factions. Suddenly beryllium ore could have a competetative sell point pop up at Freeport 2 or Vieques Shipyard. And in that situation, once the navy hears of it they can take the chance to enforce the embargo on Bering for those who choose the quasi/unlawful choice. On the unlawful side, pirates and Xenos types might want to cash in as well.
Idea 2 seems cool but I just worry about complicated mechanics overkilling what already works. If it can be done without detriment to gameplay, then new mining techniques would be a great addition after all these years.
Idea 3 seems straightforward enough.
My own 2 cents on the Sirian Economy is that we are slowly running out of valuables to entice players into earning. The server is old and so the majority of the player base are well invested and wealthy. Sometimes even the offer of quick and easy credits isn't the most enticing thing. Since sci data came in we see another material currency arise that proves that credits are only a means to an ends, and that we want money to get stuff, and its the stuff (ships, weapons, equipment, ship features, roleplay features (like SRP ID's), etc) that players value more.
So one last shameless self plug of Sirius Wars because I believe that adopting a system like this lets us turn activity into a commodity, and pilot units again into a valueable commodity. On top of it all, it then turns RP story gains into a commodity that players essentially purchase or earn. The extra driving force of partitioning story development and making change commensurate with the rate of earning means players have many things and reasons to earn credits, aside from just money to buy ships and equipment, where so many already have most of whatever they want. When the allure of ships and stuff does wear off, turning large scale story effecting actions (like destroying or capturing a base) into a commodity steps up to fill the void. So yes I believe the future of the mod could be in selling big actions for story effect. In fact I believe and always have believed that the motivation to cause change or prevent change to events is a bigger motivating factor for players than just credits for the purpose of buying stuff.
This was proven in Omega-49, as not only were fast credits part of the draw, but the chance to help the Zoner cause, or Bretonian one was a big one that got players to log.