Not sure if i can call this a modification, but let's keep that for now.
After a couple of hours to attempt to link my 06 base TL's HomeLink to work with our LiftMaster Security 2.0+ garage opener, then I learned it is compatible with our garage opener, which left me with the following options:
1. Buy the bridge from HomeLink
2. Clip the garage remote to the visor like my other cars
and i had been thinking for option 3. Finally I picked up an used remote locally, and the HomeLink board from an 08 based TL. I started the operation - solder these two items together, make connections, which will transfer the connected signal from one to another.
Basically, I connected the two buttons from the two boards, when the HomeLink designated button is pressed, the same will occur at the LiftMaster remote, making a complete circuit.
Appears the LifeMaster remote fits perfectly inside the HomeLink housing. I used 22 gauge wires that left over from my previous projects.
Hope this can help someone.

 

That's a pretty cool hack. Nice post. Thanks for sharing!