My lawyer friend isn't the one who said I don't need to file 8854, she only advised I provide some form of statement even without the need for the form. I came to that conclusion myself by reading the instructions for form 8854, which state the following:
" Purpose of Form
Expatriation tax provisions apply to U.S. citizens who have relinquished their citizenship and long-term residents who have ended their residency (expatriated). Form 8854 is used by individuals who have expatriated on or after June 4, 2004.
The date on which you are considered to have expatriated determines which Parts of the form you must complete. You are considered to have expatriated on the date you relinquished your citizenship (in the case of a former citizen) or terminated your long-term residency status (in the case of a former U.S. resident). If you expatriated after June 3, 2004, and before June 17, 2008, see the relevant section under General Instructions and complete Parts I, II, and V. If you expatriated after June 16, 2008, and before January 1, 2017, see the relevant section under General Instructions and complete Parts I and III. If you expatriated in 2017, complete Parts I, IV, and V.
Expatriation. Expatriation includes the acts of relinquishing U.S. citizenship and terminating long-term residency.
"
So if I'm not a long-term resident, terminating my permanent residency does not constitute an expatriating act and expatriation tax provisions do not apply to me. And:
" Who Must File
You must file your initial Form 8854 if you relinquished your U.S. citizenship or you are an LTR and terminated your residency status.
You must file your annual Form 8854 if you expatriated before 2017 and you:
Deferred the payment of tax, Have an item of eligible deferred compensation, or Have an interest in a nongrantor trust. "
All from https://www.irs.gov/instructions/i8854
Based on these instructions, I do not have to file form 8854. I've held a green card in 5 consecutive fiscal years - less than 8 - which does exempt me of this obligation. My total income before the November date on the I-407 is zero, and my US-sourced income after that date will also be zero (less than 7000 CHF to be earned in Switzerland by Dec 31st).
Based on these documents I have no need to file a 8854 or even a 1040 of any kind, but I am uneasy leaving things without some dated statement that can prove I am beyond the IRS' reach.