I apologize in advance for not having any sketches for those that are visual people but hopefully I can provide a decent-enough description for what is a pretty standard kitchen layout for a builders-grade home.
I have a pony wall in our small eat-in dining room/kitchen area. On the kitchen side it has lower cabinets and the dishwasher and a countertop. On the dining room side it's plain drywall and it's topped with a laminate bar height bar that measures 76X16.

We bought a counter height table and have no bar stools and no use for them. In the 9 1/2 years we've lived here we've never used the bar except as a catch-all or a place for the spread when we entertain. We've lived here 9 1/2 years and have never had them even when our dining table was far smaller so I want to fabricate a counter height fold-down surface on the dining room side so the extra dining chairs can go there for eating or it can be folded down when we open the leaf in the table to make more open space. I also like having more space for food when we have guests as well and do not wish to lose that function at all.There are no upper cabinets.

There are outlets on the kitchen side on the bit of wall that extends up to the bar. A couple years ago I installed a tile back splash without really thinking about future improvements in the kitchen :-/ so when I remove the bar top I know I'll have the tile to contend with.

My concerns are numerous!
First, I have no idea how this bar top was installed so I'm a little reticent to take a sledge hammer to it. It has no corbel support. The bar appears to be glued to the wall the pony wall is attached to, and the counter top looks like it was built down around the pony wall for support, but is likely glued to the pony wall as well.

When I build the pony wall top I will have to fabricate something to extend down on the kitchen side to cover the rough edge of the tile.

I want to make the new top of the pony wall just big enough to cover the top with a waterfall edge on the dining room side that extends down to the fold-down bar at counter height. This will eliminate or severely restrict our ability to use it as a catch-all and be place for display or just clear, clean space. Something I need so much!

For support of the fold-down bar there will be corbels that fold out. When the bar is folded down, my desired result is that it will be flush with the waterfall edge.

I'd like to use wood. I was thinking of using 2Xsomething Douglas Fir glued side by side with a stringer piece in the back (placed between 4 corbels). In my searches I've have seen many hinges and supports and really think the best (easiest) and most cost effective way to handle the job is with piano hinges.

Also, I want to create an access door on the dining room side of the wall to some unreachable cabinets from the kitchen side. I'm installing 60' board and batten wainscoting in the dining room and plan to cover the pony wall up to the bar as well. This will also hide any potential damage done to the wall in removal of the bar top.

I need advice on how to approach the project. Most heavy on my mind is the bar demo and support of the fold-down bar I have in mind. My budget and expertise are limited and pretty modest so those are big considerations as well.

Thanks in advance!!