By "pan-pseudo-signature" I mean that a sole spontaneous spellcaster's entire repertoire working almost like signature spells, except only for heightening and not "downcasting" (such limitations extant as to not completely nullify the "signature spell" rule and that Bard 20 feat in APG).
Would making this default, in tradeoff for making all prepared spellcasters getting a flexible spellcasting w/o the cantrip(s)/even level spell slot loss (spell collection size roughly the same), be fair enough?
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P.S. This thought was conceived when I thought of 5E's Sorcerer known spells discrimination, and thought of having all Neo-Vancian casters prepare up to half-level + Casting mod spells per day only, in contrast to spontaneous casters getting to know spells equal to at least their current level(s)...
The point is, that I believe the # of spells a flexible caster preps each day must be lower than an equal level spontaneous caster's base repertoire in order for both types to have a niche for being selected.