Shall we count the reasons?
1) How do you "tow" a planetary sized body? Hint--Larry Niven had a proposal in the late 1970s novel A World Out of Time--you put a big rocket engine into a medium sized gas/ice giant (I forget if it was Neptune or Uranus) and blasting away its volatiles as reaction mass, shove that around as a big tow mass. Using clever astrodynamics pool shots, you gravitationally tow your target. Easy peasy, eh? Except that bringing a large moon in close to Earth involves bringing Earth into the tidal field of this dirigible big planet and messing with its orbital dynamics too. I'll wait patiently while you go make a fusion powered rocket the size of Mars, embed it in Uranus's core, and still more patiently while you do the math for your pool shot, fill out the environmental impact statements for your close passages by Earth, and then over a period of several centuries maneuver the tractor planet around and wait for your pool shots to roll stuff into place.
Obviously if we can move Titan around this way, we could probably move Venus and Mars too, pulling the former out to Earth orbit and the latter in to it. Probably messing around with the mass distribution of the planets, heck, even shifting Titan to Earth orbit, never mind the general muddying of the waters caused by zooming Uranus hither and yon, will mess up the balance of the planets and send them all into chaotic mutual perturbations. Yes, I found that kind of incredible myself, but it was what put paid to the ASB Mars replaced by duplicate of Earth thread about a year back--some scientists did heavy supercomputer computations on the assumption of swapping Mars and Earth and discovered that the whole inner system (except Venus) goes completely haywire within a million years or so. Apparently rather than the inner planets being subject to only subtle perturbations, cumulative effects of small perturbations snowball rather than damp out, and the past 5 or 7 billion years of stability relate more to having stumbled by sheer chance into a metastable configuration rather than robust dynamic stability. Of course systems will tend to find such chance equilibria per basic chaos theory considerations, but that is a far cry from saying the system is stable. Running Uranus through the system just once is probably plenty to throw all the inner planets into chaos and they will take tens or hundreds of millions of years to sort it out again by which time one or more is probably going to be ejected into deep interstellar space. So once we start moving planets or even just large moons around we are committed to forecasting the perturbations and correcting them until the end of time or whenever we decide to abandon Sol system to its fate. Or our ability to stay on top of things goes into abeyance and the chaos spirals out of control belatedly.
2) Titan is a large moon--considerably more massive than Luna. Therefore we have to park it a lot farther out from Earth than Luna is or suffer severe tidal issues, meanwhile it is not spinning at a rate consistent with being tidally locked to Earth at a more distant orbit than Luna, so it will suffer tidal disruption. It helps to move it outward, but meanwhile, it might be necessary to place it beyond Earth's "Hill Sphere," the zone in which gravitational attraction to Earth is stronger than the tidal divergence relative to the Sun's tide on Earth--beyond that horizon, objects cannot be said to be in orbit around Earth at all, though they can be linked to Earth by resonance orbits.
3) much of the features that make Titan interesting relate to its chilly location in the Solar system, parked way out at Saturn. Bring it to 1 AU and it gets 100 times the incident Solar heating and its temperature would increase accordingly. An object more massive than Luna but so much less dense its surface gravity is actually lower retains four or five atmosphere's surface pressure of mostly nitrogen gas interlaced with some hydrocarbons mainly because it is so cold. We haven't been talking about how long Luna's thick terraformed or ASB endowed atmosphere could last; I would intuitively guess it would be many thousands of years before the pressure fell noticeably on the surface. Titan has a deeper well, and its nitrogen atmosphere must be warmed up to the 300 K range from around 100 K, before it starts losing gas at the same rate as Luna would. Meanwhile, once it starts to warm up like that, the surface materials are made of mostly ice--water ice and other ices. These will melt and we wind up with a big blob of liquid with all the solid materials sinking down into the core.
So, not such a great plan; I prefer Titan right where it is!