The very first thing I added was the rule of 5. Any spell craft roll that is five over its intended target will only cost the characters 1/2 the MEP needed to cast the spell. The character cannot attempt the roll unless he has enough MEP to cast the spell normally.
My second addition to the rules is that any arcanist over the level of 5 can cast 0 level spells at the cost of 0 MEP. A spell crafting roll is still made as normal. but MEP is never spent. And this level the arcanist is skilled enough that most 0 level spells are muscle memory and so elementary they are at little if not no risk to the arcanist.
This final rule is only available after level five. The arcanist may choose to "push" a spell that scales. For example a spell that does 1d6 dmg per arcanist level. The arcanist can choose to cast the spell as if it were 1-3 levels higher than he is. Each "pushed" level adds a CL of 2 per level rather than 1. The MEP cost will be equal to the final level of the spell plus levels it was pushed plus one.
For example an arcanist is casting a spell that is level 3 that does 1d6 damage per level of the caster. The situation is dire so the arcanist decides to "push" his power up three levels. Making his spell as if cast by a level 6 arcanist. The CL of the spellcraft roll would be 3 + 6 +1. Three for the normal casting of a third level spell, And six more for twice the level the spell was pushed. MEP cost will be 10.