I hope this makes it easier.
You can automate the synced lfo in Massive. Although I'm not sure if it's because of the 1.1.4 massive update or Live 8 making more parameters available. Live 7 only allowed 120 or so parameters to be controlled through the midi instrument config panel. If I remember right.
You can try one of two ways...
A. Load NI Massive 1.1.4, then go to the 5 LFO tab. Once there simply activate the "sync" box, click in the ratio box of the value you wish to automate. (top or bottom) i.e. 1, 2, 4, 8, 12, 16 etc... That should cause it to show up in In your midi channels automation lane in arrangement view. The values for the 4 LFO tabs are named "Modulator 5 Den, Modulator 6 Den, Modulator 7 Den, Modulator 8 Den"
B. If you do have Live 8 the midi parameters panel now has a "configure" button. Click that, it will highlight green. Then go into Massive and click the in the rate box of the value you wish to automate. It should show up in the automation lane of Massive in arrangement view. Then map your controller to the green slider or draw in your automation.
A little tip when creating synced sounds in Massive... If the "pos" box above the "sync" box is checked Massive will not be affected by the LFO unless the DAW is playing.