It comes too late, even if colonies themselves take too long to take off.
Agreed, and as long as you more or less have to have a size-6 colony before you can actually use it I don't know that there's really any way that that'll change even though you could theroetically rush finding and restoring a Hypershunt.
I already use two forges and a synchrotron on three of my five worlds (which I need to feed Military Base or High Command, the big resource hogs), so that leaves two worlds left for other items.
Six or seven colonies is well within reach using only the player character and hired administrators, and up to eleven without income penalties except during shortages is workable with enough care - colonies administered by hirelings are neither affected by nor count towards the mismanagement penalty, a fully-developed world can have up to +17 stability (+6 base, +2 Domain-era Comm Relay, +1 domestic goods, +1 luxury goods, +1 Ground Defenses, +2 Military Base or High Command, +3 Star Fortress, +1 Population & Infrastructure "improvements"), and pirate hostile activity only cares about the largest most stable colony while other stability-related penalties only come into play at less than 5 stability, so one hireling governing a size-6 planet neuters passive pirate hostile activity while the player character administers all other size-6 worlds and the other two hirelings manage developing worlds until the player character's mismanagement penalty becomes too high to add another size-6 world without reducing stability below 5, giving up to five colonies administered by the player character even with Commerce and Free Port or up to eight with neither Commerce nor Free Port. Dropping the Population & Infrastructure "improvements" and swapping the Domain-era Comm Relay for a Makeshift Comm Relay costs you a planet, but that still leaves you with four to seven colonies managed by the player character plus the three administered by hirelings before PC-governed colony stability drops unacceptably low.
Tap should give +4 interest like everything else.
Honestly, considering how thin the margins are on most industries when they're not being boosted by something, I'm not sure that it'd really be worth using even at +4 interest if you're trying to avoid generating Path cells; roughly doubling the gross income of an existing industry or increasing the colony income multiplier by 50 points looks far more appealing to me than adding another barely-profitable industry to the planet.