Currently Daedric Summoning is most noticeable through the number of Toggle abilities it has. Although 1.6.2 has made pets better, it has not addressed the fundamental problem with toggles - which is that they do not make for a dynamic and interesting play-style as they are inherently a static ability (basically a passive effect).
In addition most Toggles tend to be placed on both bars to prevent the pet / ability deactivating on a weapon swap. This coupled with a spell cost, a reduction in maximum magicka, and a cast time (for Twilight) means that the Toggled abilities must be very good to be worth the investment...
My suggestion:
In order to make the investment in toggled abilities worth-while and to increase the range of dynamic game-play options, all toggles that are placed on both bars should gain an active ability (a little like defensive posture has a passive effect from being slotted and an active). The initial activation of the ability sets the toggle on and to actively detoggle it is a CTRL+ability (or similar dual key-press by default]). Any use of the normal activation key after the toggle has been set on, activates a secondary ability based on the nature of the skill.
Example abilities are
Familiar: Activation ability: Daedric explosion
Active ability: AoE explosion at familiar location. Costs magicka.
Clanfear: Activation ability: Tail swipe.
Active ability: AoE knockdown + damage (equiv to Daedric explosion) at clanfear location.
Unstable Familiar: Activation ability: Unstable explosion
Active ability: Causes an AoE explosion + stun at familiar location. Costs magicka.
Winged Twilight: Activation ability: Azura's light
Active ability: Performs a heal on caster. Costs magicka
Restoring Twilight: Activation ability: Azura's light
Active ability as Winged Twilight. Morph provides a magicka regeneration aura
Twilight Matriarch: Activation ability: Azura's light
Active ability as Winged Twilight (cost stamina?). Morph provides a stamina regeneration aura
Bound Armour: Activation ability: Azura's nullification sphere
Active ability: Absorb next magicka attack, replenishes magicka based on damage absorbed. Costs stamina
Bound Aegis: Activation ability: Azura's nullification sphere
Active ability: As Bound Armour
Bound Armament: Activation ability: Azura's nullification shield
Active ability: Absorb next magicka attack, replenishes stamina based on damage absorbed. Costs magicka
Note that other toggles in game would need the same treatment (such as Mage Light), but that is outside the scope of this discussion / reimagining as this is about sorcerer class abilities.
In addition sorcerers do not have any good group buffs / capabilities. A solution is to rework the daedric summoning line such that it can also be used as a support line. This could be done through the following changes:
Change Expert Summoner:
As it is this passive is weak - in that it only affects 1/2 of the skill tree abilities. It does nothing for Wards, Bound Armour, or Curses. So if we have to have a pet buff, lets have a proper per buff.
Suggestion: All Pets receive additional health from Expert Summoner as well as additional damage. Twilights gain a chain lightning effect (minor AoE, +2 targets). Familiars gain a charge ability. Atronach gains range and taunt (if sorcerer is only one on hate table).
Change Rebate to Symbiosis
This passive does nothing until the pet dies - and pets are only 2 out of the 5 skills in the tree. So this passive is really, really, really poor. It doesn't increase DPS, it doesn't really help with magicka sustainment, it doesn't do anything unless your pet dies... and the chances are that only one would be recast in combat anyway as the other has a cast time. So just remove the max magicka penalty from the summons (the Toggle is enough of a penalty) and we can have a decent passive here.
Suggestion: Symbiosis
Pets receives sorcerer's current major and minor buffs at 50% / 100% strength. Unless our pets already gain our buffs (which I don't think they do)
Change Daedric Protection:
The health regeneration is not a great passive for most sorcerers, it helps tanks somewhat, if they have any abilities from this line. A straight bonus to maximum health for every ability on the bar would be better, maybe 5%.
Change Conjured Ward
Conjured Ward can ward the sorcerer and up to 2 additional allies of the sorcerer.
If the sorcerer has pets active these are the first allies warded.
If the sorcerer has placed a daedric curse, then conjured ward will affect the two closest allies to the target of the curse (unless a pet has taken one or more of these wards), otherwise they will affect those closest to the sorcerer.
Conjured wards cast from multiple sorcerers do not stack.
This would allow sorcerer healers to be more effective (i.e. perform bubble healing).
Change Daedric Curse
Make this an actual DoT with a detonation at the end of the duration, such that other abilities can proc.
Change Daedric Prey
The recipients of a Conjured Ward, receive the benefits of a symbiotic relationship with the sorcerer (i.e. get the symbiosis passive buffs) for the duration of the ward only (note this is not quite as powerful as it first seems as these buffs will drop as soon as the ward does, do not stack and as the ward is unaffected by armour/spell resist buffs, these will not affect the recipient in real terms).