Leave Zhonyas as is
Taking off that much AP will be a death sentence for the item, some extra mana and some extra CDR wouldn't come close to making up for the AP cut. Let me spell it out for you rito
See there's two mage varients, DPS/DoT and Burst mages
A burst mage would want AP first and foremost with CDR and mana being a close second and third A DPS/DoT mage would want more CDR and Mana as opposed to AP
The playsyle of a burst mage is to blow all their spells and hope to kill the target with everything they have. a DPS/DoT playstle is to just "Machine gun" or wittle down an opponent similer to an ADC with its AAs
Out of both mage variants Zhonyas is bought almost exclusivly on burst mages because the active synergies with their playstyle a DPS/DoT mage would find the Zhonyas active a hidderance because that's 2.5 seconds not wittling down an enemy, the only DPS/DoT mages that buy Zhonyas are the ones who can continue to DPS while in Zhonyas (
) changing Zhonyas would make it a useless item for burst mages (Since maximising AP is the main priority for a burst mage, it's why their build is almost locked to
and ether
or
) and useless for DPS/DoT mages besides 2 (Maybe 3) because the active wouldn't do anything for them.
Not only that but it would essentially give a mage no burst defense, especially given out of the 3 it's already the weakest
Mage burst item, can move freely, gains lifesteal and spellvamp when the shield activates
General burst item, can move freely, increased base AD and gains a shield based on 30% of max health
General burst item, Can't move when active, 2.5 seconds of invulnerability
I know some people will retort that
is an anti-burst item but here's the difference between it and those, for one Seraph needs to get to the point to transform so until then you don't have an anti-burst item
For two if your OOM with any of the 3 other items they work fine but with the Seraph if your OOM it's shield is useless
All in all there are PLENTY of mage items which could be used instead for this which are never built except for certain champions or circumstances
so why they want to change Zhonyas is beyond me