Thought this might be more appropriate than posting in your newly created thread... If not, feel free to merge/delete this.
So... I have an idea about basic design principles: You said your aim with this system is to be able to recreate every spell in the PHB using Seeds. But why bother? It's not like the PHB spells were balanced at all, anyway. Many of them are useless, and others far stronger than needed. The reasons for this vary (some are too specialized, for example).
So why not instead use them as a kind of general guideline for the types of effects you want to create, but then give yourself the freedom to generate your seeds/effects based upon what you want casters to be able to do? You don't have to specifically recreate the D&D spells using a different mechanic, and there is little benefit in trying to (IMO).
Your Illusionary seed might be a good example. Instead of saying "you can recreate any illusion spell with a level = 2xSP spent", how about saying "for 1 spell point, you can create an illusion that affects only hearing, scent, taste or touch. For 2 spell points, you can effect vision. You can combine these to effect more than one sense (2+1 = sight + hearing, for example). Have the original area and range be very small (as with your original spell seeds), and if you want to affect a bigger area/more creatures, you have to augment it.
You could add something like the more points you spend, then the less obvious an illusion it is (so for only 1 spell point, you can create concealment (i.e. it has holes in it), for 3 you can create total concealment, etc).
Your existing Elemental seeds also follow this kind of idea (very generic, do X damage to one creature, if you want more you need to augment).