you are thinking purely in mechanical terms of characters and dice pools and limits.
This is not what Wild Spirits are about. (again, this is mostly a throw back to earlier editions.... and would take a long time to explain....)
You are missing the forest for the trees.....
but you probably won't be satisfied until you get some background on what is happening here. So here is the background in a nut shell:
From Editions 1 to 3 magic was split into 3 different camps, with little overlap. The camps were:
Hermetic magic.
Physical Magic (Physical Adepts)
Shamanic Magic.
Hermetic magic systems ran off of mental stats, had astral travel, summoned Elementals in a ritual casting.
Physical Magic is pretty much unchanged through the editions, except for the expansion of mystic adepts...
Shamanic magic ran off of personality stats, had astral travel, and could summon Spirits on the fly.
The BIG difference was in what was a spirit and what was an elemental. Spirits showed independent thought and Sapience, but where tied to a location.
A hearth spirit couldn't ever leave a house for example, They were tied and bound to the limits of their domain. Which really didn't bother a Shaman too much ass he could just whip up a new one in the new domain in a few seconds.
Elementals where more like robots, in that they had no personality and where pretty mindless, but could go anywhere.
Things stayed pretty separate until FASA died and FanPro took over Shadowrun. One of the things they did to "Streamline" the game was fuse the Hermetic and Shamanic traditions into one collective whole divided only by resistance stats and combine elementals and Spirits in just "spirits". and to explain this away in the Lore, they gave us:
Universal Magical Theory!
The premise of which is that since all magic comes from Mana, its all the same! all that changes is how you use it
Which, when you get right down to it, just really screwed not only with the lore, but with game mechanics they later tried to introduce by way of "Traditions".... after all, how can every tradition re-invent the "wheel" when its a "wheel"..... (UMT basically says that traditions don't matter.....)
Now what you are seeing is a slow, in game correction of the UMT in game by saying "hey, we fucked up and don't know as much as we thought we did!"....As such, expect the rules for wild spirits and more info on them to trickle out in other books over the months years and editions, but I wouldn't expect anything overnight.
*****
In short, they are there as an option for the GM and not really there for the players to just jump in and pick up and use. For that there are the regular spirits that are supported by UMT that every mage knows and the player to abuse as normal.
Some things are just not there for the player's investment (at least not with out direct GM approval)....
Corruption magic
Blood magic
insect/shadow/wild/free spirits
AIs
These are generally the realms of the GM to use and interact with the players, and not for the players themselves (again, without direct GM approval)
edited for spelling