If it is a custom wedding then the couple will have a room block. Hopefully, they would spread that room block to from the low cost to moderate to premium resort. i.e all-star, POR, GF... (we did that for our guests)
If it is an intimate, there is no room block so it would not hurt to ask Disney.
Also, if there are other brides on here getting married at the same time AND they need people to fill their room block.. you may be able to take avantage of that. Doesn't hurt to ask.
Hope that helps.