major dress Regret!! Help :(

Ok first of all, your dress is beautiful and looks amazing on you!

I think a key thing to ask yourself is whether you care about the beading showing through the dress. Because if you add layers over it to make the skirt fuller, you will likely lose that feature. If you don't want to do that, then you could try a ballgown overskirt. They are just separate skirts that you put on right over your existing dress without having to modify it. You would then have the option of wearing it for the ceremony (to capture that big, full skirt moment), then removing it for your reception (to reveal the beaded underlay).

I agree with possibly trying a petticoat to add some volume underneath, but I do love it the way it is, and I adore that underskirt.

I really love your dress as is. You can add a crinoline slip, hoop skirt under the lining. ( I think) to create a more full A line shape but you couldnt have a slit. I dont think i have seen any full skirts with a slit unless it was made of Satin. If you really want that Ballgown Princess poof, perhaps you could try to shop around for one on discounted cites like Still white, Poshmark, Mercari, Hebeos, Missacc. A lot offer dress selling services and tons of discounted brand new dresses. Selling a dress can be a headache and you might not get the money you put into it, out of it.

However i think you chose the dress you did because you love it. Work with it.

If you're leaning towards starting from scratch with the dress, just know you won't get out of it what you paid, even if you still technically have the tags on it. Alterations are an option but be aware of how expensive they can be, especially for something like adding a slit if they're doing both layers of fabric, and those layers have beading and lace that need an experienced, talented hand. Are you sure you're wanting a slit and more volume in your skirt? I can only imagine that possible (in this dress) if you add petticoat layers and then have BOTH layers of dress AND part of the petticoat layers cut for the slit and with the way fluffy petticoats go, you may end up with volume poking out of the slit. You might have a very particular dress design in mind but it sounds unique and might not be copy-able unless done by a real professional.

Cece had the best idea so far, with the skirt that goes over the existing fabric. Petticoats are a nice idea but there's the potential if your dress has a fitted waist with no stretch (which is what it looks like) that fabric may bunch up in a way that doesn't look or feel flattering since it's caught in an A-line sheath not meant to really move. You may have to try different ones on to find what you like- and it could be the least expensive option!- but that dress was made to be A-line and may lack the lightness and give that petticoats and hoop skirts need to give you the volume you like without looking overly stuffed.

In short...if you can afford it, do whatever makes your heart flutter the most. Advice is nice but if you're already leaning a certain way or hoping the advice points you in a particular way, you kinda' know what you want and that's a good thing!