General Discussion
I read an interesting article in the Best of the Rifter book regarding spell casting, the original was from Rifter #21 I think. This idea originated back when you could only cast 2 spells a round, and naturally the GM ran into the usual problems when you have a high level caster that takes 7.5seconds to cast a spell when being assaulted by 4 people.
Considering the idea is in the Best of the Rifter I think they may have used it as a starting point in Palladium's move to an actions/spell system, like in the Ultimate Edition. Though I do like this idea better as the problem with actions/spell system is that it treats all spell-casters essentially the same regardless of level; hence Gandalf the White is the same as Smedrick the Wizard.
Anyway, the idea is that depending on your casting class category (dedicated/specialist/dabbler) you can channel X-number of PPE/XP level per action/attack. In the original article this was 5PPE/level for dedicated casters like Ley Line Walkers, for specialists like TechnoWizards and Shifters it is 5PPE/Level for spells in their focus field or 3PPE/lvl outside. Finally, the Dabblers are like Priests or Magic Super Spies, and they get 3PPE/lvl.
On top of those levels the author suggests Supernaturals add 2PPE/Level to the above, and Creatures of Magic (Dragons, Faeries, etc) add 5PPE/lvl to the above totals, due to their magically-infused natures. Similarly for those few NPC/RCC/OCC's that gave extra spell attacks you could just say they can channel X more PPE for each of their regular attacks.
I'm not sure if the author was using the old 2att/melee base or the newer 4att/melee system. May need to play around with PPE/Level amounts a little to adjust, but I think a system like this works better than an arbitrary # of actions to cast a spell of X level, and it makes high level casters that must more impressive since they can rip-out the big guns very quickly. Meanwhile your level 1 ley line walker, though technically capable of casting Annihilate, wouldn't do so because it'd take him forever.
The PPE costs of spells in Rifts doesn't always trend linearly with level, for example level 6 and 7 spell have a lot of overlap in the 20PPE range, but the heavy hitters are usually reflected in PPE cost. I mean a spell like Annihilate costs 600PPE (300PPE for some), and thus even Vrryl would need 4 actions to cast it with the above numbers (10PPE X 9lvl = 90PPE/action x 4 = 360PPE), but he could cast most 9~10 level spells in a single action.
Thus it becomes a more strategic game for higher level casters; balancing their PPE reserves with the combat around them (dodging, positioning, etc). Since there's so much magic in this group figured this would be a good discussion, especially since the casting system was changing regardless.