The two WC teams should play best of 3 series for two reasons, IMO,
1) Don't like the idea of winning one game or out, this isn't the NFL playoffs, MLB teams play 162 reg season games. Play a 3 game set and then begin the LDS as soon as possible afterwards (1-2 days) in order to help "penalize" the WC winner by allowing less breathing room as possible for them to rest their pitching staff.
2) by having a 3 game WC series you at least give a team (or two) which may have a BETTER record than a division winner a fairer chance to advance in a 3 game series instead of getting "eliminated" by losing 1/1 games after a six month 162 game schedule.
Case in point.....this year in the N.L - Pirates/Cubs. BOTH of those clubs deserved a more fair chance to advance - MLB just has to come to terms and "properly" handle situations where one or more (WC) teams have won MORE games than division "winners" who were able to win their divisions with less total wins.
Just because a team was able to win their division in a given year with 87-89 wins or so we should NOT shortchange "WC" teams which may have won well over 90 games with a "one and done" scenario.
If MLB wants to implement some type of "handicap" after the WC series to reward a division winner that's fine with me. Have the LDS begin immediately afterwards or as soon as possible while a division winner has already had a couple days to rest and set up their P rotations, and/or drastically limit the amount of home games the WC winner has in LDS.
Schedule a couple of doubleheaders during the reg season....be careful, there could be rainouts and some teams could really be up against it by having to burn up their pitching staffs in a FEW doubleheaders just because they had the misfortune of getting 3 or 4 rainouts combined with the pre-scheduled doubleheaders.
I guess 2-3 pre-scheduled doubleheaders should be the max...or maybe MLB should just begin the reg season a week or so earlier and be done with it.