I'm looking more at template than power atm

It's an extreme hoop to jump through. Either it's changeling tribal, or you have to have at least 3 creatures in play that don't have much synergy between them. Difficult hoop suggests that the payoff should be high.

It is probably a bit easier to do in a janky limited deck; which is kinda funny. But also pulls against the power level.

But how's the template? Regardless of costs I'm wondering how I should be piecing it together.

For the record this is all for the limited first, I've little interest in meshing the set with anything changeling

I think it works. Most magic would probably put the collaborate on the effect rather than the cost though. Partly because it would have a lot more of an effect on the game.

Why doesn't this just reduce the equip cost the way Ghostfire Blade does?

Equip legendary creature 3

Equip 7

As per black blade reforged.

Either is fine it seems, I'll probably switch to the ghostfire template later

Except that you cannot use the Blackblade wording because the condition for the reduced cost is not inherent to the creature being equipped, but some other board state. Which is why the current wording on that card looks... unfortunate. (It also doesn't help that you put all the equip abilities at the top rather than below the static and triggered abilities that don't modify equip itself, where they are on a regular Equipment.)

Really, if you wanted this to somehow work at all with two equip abilities, it would probably more like:

> Collaborate -- As long as there are five or more creature types among creatures you control, ~ has equip .

But at that point you may as well replace the "~ has equip " with the cost reduction clause.