I suffer from an ailment; I create great walls of text.
Yes, there is a similarity to totemists; but I wouldn't go with daily pacts - you either have a contract with a creature or you don't, for the most part. A year and a day would be a typical contract time, in fiction, although 'for one day' could be a smart way for a DM to try out allowing a creature - if it's too powerful, it won't agree to further pacts.
What do you think of using a Concentration check at casting time, and, say, taking unavoidable virtual nonlethal damage on failure? That way, trying to cast a too powerful, too difficult spell, might knock a caster unconscious even? Or maybe exhausted/fatigued pattern?
I managed to read up on Binders; The effectively do a transform-lite to the target creature (and that's what vestiges are; creatures sans attributes or skills)
So... Instead of binding creatures, you regardless make a pact; DC should equal 15 + target creature's CR, for the most part. This only allows you to draw upon the creature in actions, unlike binders who let the creatures effectively live inside themselves.
The roll would be d20 + class level + CHA modifier, with +2 synergy from having 5 ranks in diplomacy, and +4 at 10 ranks.
Unlike Binders, you must actually know about the creature, using an appropriate knowledge check; Failure of 4 or less increases the DC by 1 each, with as usual, failing by 5 or more means you either don't know enough of the creature, or that you attract something you'd rather not. Each 5 over DC gives you +1 to the pact / contract check.
Not binding them leaves you with some further freedom: You can summon your patron's influence on the world in other places besides your immediate vicinity. This increases the DC of crafting a spell.
Your magic ability would be something like your class level + your charisma modifier, so typically 4 at level 1.
The following may be a bit too complicated, although I'm not sure...
[spoiler]
Let's say, f'r ex, casting time would use a default cost of standard action: Going faster - move, swift, immediate or free, would increase the cost by 2, 4 ,8, or 16 pts. Increasing the casting time would decrease the cost by first 1, to full-round action, then 2 for a full round, 3 for 2 rounds, 4 for 3 rounds, 5 for 1 min, then 6 for 10 min and 7 for 1 hour, which would be the maximum casting time.
Increasing a spell's duration would work similarily - 0 immediate, 1-3, 1-3 rds, 4 1 rd/lv, 6 1min/lv, 8 10min/lv,
Range would use cost of 0 for personal, 1 for touch, 2 for short, 4 for medium, 6 for long.
We don't need to worry about areas, as those depend on the patron's abilities.
SU abilities cost 6 more, SP 12, and actual spells 18.
So,
as a rule of thumb, we can cast spells with magic power of 3-6 at first level; our power is 4, and our maximum result for the spellcraft check (used for, y'know, crafting a spell) would likely be 26-27, which is
10 more than a base DC of 16.
although making a more complex spell should increase the craft DC...
[/spoiler]
a standard action offensive spell accessible at first level, on short range, could be a small fire elemental's slam attack, +3, 1d4 +1d4 fire and ref dc 11 vs. 1d4 rounds of Burn.
Magic cost of 1 (cr of a small elemental) and +2 for short range.
It's probably good to allow either Aid Another (+2 to hit) by increasing the cost to +6, or doubling the damage (summoning the power of two elementals).
Also, typically you could gain <element> mastery for 1 round / level, or an Earth Elemental's Natural AC of +7 (which, for an unarmored mage is only about equal to a fighter with scale mail + shield, which is okay considering all the nerfs mages get with this mechanic ).
I guess it would be good to list what a mage could get without input from a DM - summoning a creature's attack, or one of it's natural attributes (nat ac, darkvision, movement mode) on self, or using one of it's EX or SU abilities....
That being said, a monster-ability gaining virtual totemist is also interesting... PCs getting monster abilities IS effectively the whole mechanic of both MoI and the Binder.