My first pick would be to put your V on Jelwood. Pendlebury and Swan both have great records against North, but I think I'd use my C on Minson (or Libba!
).
As to Libba/Bennell, keeping in mind this trade is for one match only, and not long term:
Libba - has averaged 114.8 since round 14. In round 14 when he last played Melbourne, he scored 163 in a losing team!
Bennell - has beaten up some average/poor teams. 119 and 121 against Bris and Melb earlier in the season, and in the last 4 weeks has gone 123, 122, 137 against WC, Melb and Port. He should be able to go big against GWS.
Dangerfield - Had a hot spell between rounds 12 and 15 with 150, 141, 136 but has only averaged 96.6 since then!
Griffen - Ridiculously hot streak between rounds 7 and 14, where he averaged 143.4! Since then he has averaged 106.0, so in the last 9 games Libba is averaging around 9 higher, and Griffen will get the McKenzie tag.
Watson - because of the great unknown, I'd avoid anybody from Essendon right now. He did score 166 earlier in the year against Richmond, and is only averaging 106.0 in his last 7, but if you take out the injury affected 24 in round 15, that jumps up to 119.7. Just too many question marks for mine.