He's departing from along my own commute route. The problem is there's no good east-west way between most of Vermont and the Thruway/Northway. Sure, US 4 is freeway west of Rutland, but that dies at the state line. I'd rather slit my wrist along NY 7 in Troy and Brunswick than deal with Fort Ann and the western NY 149 terminus.
A further complication, but one he (and I) will just have to live with, is just getting out of Morrisville. Both 100 between Morrisville and Stowe and 15 through Morristown have repaving projects underway. 15, in point of fact, is down to bare dirt through Morristown (and they were ripping up the pavement at 15/100 as I left work last night).
Given the trailer, my suggestion is to get down to Rutland via whatever route you're most comfortable with (on that note, I've heard 100 towards Killington is ripped up too), then continue on US 7 south to Bennington, then VT 279/NY 7 over the Albany region. Despite it likely being afternoon rush hour by then, I'd suggest taking 787 through Albany and picking up the Thruway at Exit 23. You'll at least save a little toll that way. And this route avoids Massachusetts entirely.