Here's my 2 cents on the subject (and that's all it is worth!)...
Option 1 - You buy 30 pts at BWV through resale at $84/pt. Total cost would be approximately $2,870 ($84 * 30pts +/- $350 closing costs). Other assumptions are you get your desired UY and it passes ROFR.
Option 2 - You buy 30 pts at BWV direct from Disney at $106/pt. Total cost is $3,180. You retain same UY as your current 70 point contract and the transfer is done immediately.
Option 3a) - You sell your 70 point contract at $82/pt. Total receipt is approximately $5,166 ($82 * 70pts less $574 sales commission). Assumes 10% sales commission and purchaser pays closing costs. Option 3b) - You purchase a 100 pt contract at $80/pt. Total cost would be approximately $8,640 ($80 * 100 +/- $640 closing costs). Again assumes you get your desired UY and it passes ROFR. Total net costs = $3,474 ($8,640 - 5,166).
There are a lot of assumptions in these scenarios. Time is a big factor as well in buying & selling through resale. Option 3 where you would sell your existing contract and then purchase another larger contract would be the least desirable using the stated assumptions. Commissions and closing costs on both transactions hit hard. With that said, then the choice between Option 1 and 2 depends on whether it is worth the +/- $300 extra cost to purchase direct vs resale. IMHO, a direct purchase from Disney would be my choice (don't forget the 2 cent value of my opinion) so you can keep the same UY and avoid the potential frustration of ROFR plus the time difference. Good luck in whatever you decide.