A treaty sloop could combine light guns with floatplane reconnaissance

Could a 2,000-ton treaty vessel carry four-inch-class guns, three floatplanes, and two catapults?

Yes in principle; the light gun battery was practical, though the aviation arrangement would be the tighter design problem.

The proposed ship was technically buildable within the broad concept described. Multiple four-inch-class weapons were already normal on sloops, so the gun battery itself was not disqualifying. The harder problem was fitting the floatplanes and catapults within the available displacement and deck space. Aviation facilities and armament would have to compete for a treaty hull's limited volume.