You have the right parts and idea to start. I always liked the "third wheel" concept, combined with one matching Hobie scupper cart (or one of those under the hull wheeleez carts like Tom uses).
If you want to keep things simple, just use a Hobie scupper cart on one end and the wheeleez or C-TUG on the other. Folks seem happy with this. I don't know which fits in the front hatch, except for the C-TUG but the collapsable Wheeleez may fit with the 30cm tires removed. (Tom might be good enough to check this for you).
If you really want to get geeky, the front drivewell/locks look interesting. This area is somewhat reinforced already. Plus there's a steel on steel positive locking mechanism just sitting there. WTH.
You can cheaply buy the same metal axle rod that goes through your mirage drive and mount this to your wheel/support plate. Just need a way to wedge, screw or ratchet it down to take out any slack below the hull. But I would avoid anything sharp
in the scupper or drivewell areas, like the pvc tabs in the CAD.
By now you realize how heavy the TI hull is and how hard it would be to put any wheel in place, even after the the hull is supported by the rear wheels. The trick will be making it a one man job.
Three wheels would be sufficient for the AI (over-engineered) but for the TI, I wonder... But please build one, cuz if it works, us AI guys can borrow it.