Just simple math. The more people, the better it works, but we need 1 or 2 rounds after everyone in the list is lynched for us to use the information we get from the strategy.
Did you make sure to include the possibility of:
- all five randoms end up as Brotherhood (town)
- Inner Party (mafia) uses two Victory Cigarettes
- every mafia event has a few mostly-not-playing players in Brotherhood (town)
?
This would be starting with 18 Brotherhood (town), losing one at the start (NK #1), and beginning your plan with:
17 - 5 (ordered random lynches) - 5 (Inner Party NK's includes the night AFTER your plan ends) - 2 (VC's) = 17 - 12 = 5 against the initial 4 Inner Party members!
If Inner Party happens to also have any of the items like Victory Gin / Propoganda which affect voting totals (either by great luck in the outset assignment of items or via Steals in-game) then your plan might be a near instant-loss for our Brotherhood (BH)...?
There is about a 30% chance that a list of 5 per your plan ends up netting 0 Inner Party (IP)!

Even without the cigarette's and lucky-start/steals by IP we would be left with a higher-than-many-would-like chance at staring either 7-against-4 or even 5-against-4 final showdown.