Given the way that its worded, if you equipped his signature gun while you have any tools out you'd have to discard them because it has to occupy his hand slots to hit the board before the asset can offer it's ability to make up to two tools not require hand slots, right?

They changed the rules because of Mitch Brown .

From the current FAQ (v1.41):

Quote

If play ing or gaining control of an asset would put an investigator above his or her slot limit for that type of asset, the investigator must choose and discard other assets under his or her control simultaneously with the new asset entering the slot.

Previously, you had to discard the asset before you could play the new asset. Now you play the asset and check if you are above your slot limit in the moment the asset enters play (and already is active).

I guess it's the same with Detective's Colt 1911s: You can play them without discarding your Tool assets before.