a fair summon spell

In the recent times, I've been trying to come up for rules for summoning.

So you give a wizard a summoning spell and what happens?

If the scope of it is too narrow (you can summon this specific demon that does X) it becomes just a hireling or even a piece of equipment.

If the scope is too wide, you have to bargain with the GM what you can do and what you cannot. How many HP can the demon have? how much light can produce, and which color? can he pick a lock? can he summon other demons?

Usually, I don't have much problem with the last option, but for the sake of grognard's folly designer's challenge I want to come up with some rules that define it's boundaries.

I wish my dogs could be summoned so easy

The first idea that I had (as seen on previous games on this blog) was to have every wizard to have a number of bonds they could call; probably a number equal or tied to the CHA mod.

This bonds could be to things to be found in game (an animal, a talking flame, a magic item, a lake, etc) and when you summon it, is that thing's force which exerts the action, or impersonates in some form. It stills leaves open things as "how much damage/hp" but can be done in the World of Dungeons style (1d6 damage, +1d6 if is specially suited to the occasion). Which for HP would be like (roll 2d6, on doubles you get armor or something).

A bond can be broken at anytime in order to bond another thing, but you need to be in the presence of the thing to get a bond, and get a friendly reaction (use reaction rules and roleplay as needed)

I like this way because the interaction with the environment reminds me of one of my fantasy staples: The Loom videogame (where you had to walk around finding spells in things)

Loom (1989) remember lucasfilm???

But it still has too many moving pieces. ¿ How many turns last? which kind of skills does a lake have? what shit you need to befriend to pick a lock for you? :S

The second idea is much more codified:

When you summon something, take your game's equipment sheet and get the item that matches your choosing. Yes, even hirelings. Yes, even the Mansion. It takes as much HP to summon as the item's cost/10, and whatever you summon has an otherworldy flair on it. Weapons do their equivalent damage in spell (a bow is a magic missile), OR you can summon the real deal for a while, if you're proficent on it.
Very expensive things might take decades to summon, little by little. Or you might call some Expert Kobold Hirelings to build that galley for you.

Opinions, Ideas, Suggestions, etc are all welcome!

from World of Dungeons. Into the Odd's one also feels very appropiate for this approach.