Add a filter to the trade finder based on how much ISK that person has and the sell price. Just like cargo space but with ISK.

If a either of the two stations along a route have more than one buy or sell order of the same item and the price of the other buy and sell orders is close to the best than they should be added to the route.

for instance:
Jita has three buy orders for 200 mexallon (all at 1 standard deviation from each other or something)
Motsu has 1 sell order for 600 mexallon
then the units tradeable should be 600

Ex: My player is located in Hek, and eve central finds a trade from Rens to Aldrat. The profit per jump will include the number of jump from the start location (Hek) to the buy location (Rens), and add them to the number of jumps to the sell location (Aldrat).
Currently, the trade with the highest profit per jump may not actually be the best option because you have to waste time getting there; there may be a better trade, which may have a smaller profit per jump, but is much closer (and has a better overall profit per jump)

Allow the user to enter a list of items and how many of each he needs, and offer to filter by region (plus surrounding ones). And provide the cheapest and closest locations to find everything in the list. Offer to weight it more my price or distance.

I like to do some offline number crunching for manufacturing and if I could have some kind of offline database of prices it would be very helpful. I usually use Jita prices as they are the most equalized.

I would like to have highest buy order, lowest sell order, number of units sold in the last 90 days.

I want a custom page for a registered users. On that page i wish to see a customizable set of quick-look price tickers for a specific item in a particular system or region or set of regions. There should be an ability to display max, min, avg or median price on a ticker. Such, when opening this page, i will see prices in my favorite regions for my favorite items.
Tickers may appear like small banners. Something like a chart or price history is also preferred.

Manually input your accounting skill/your sales tax so you can see the true profit and how much each item will really sell for.

sort items by the profit per amount of cargo space an item takes up. therefore you can haul the most amount of items

A list of regions where prices are being uploaded from, so we can see where the gaps are, and during our travels we can make efforts to cover the areas not being uploaded, so eventually we manage to canvas all regions and have the prices uploaded. Side effect of this would be to make the less uploaded systems prices not time-out for several months, until there is another refresh.

The current upload leaders already have such high upload amounts, it'd take a good deal of effort for anyone to catch up to even make the bottom of the list. Make a separate leader board for a smaller time frame in addition to the Overall Leaders.

find the best trade between a number of regions, including trade within a region. If it is too taxing to the server, limit the number of times a person can request this.

When you find that item is no longer economically viable to trade why not remove it instead of seeing it over and over and over again?

I really want to use the data uploader, but the mac version is broken. Please fix it, I know I can use the source version, but it looks really complicated and I'm not that technical, so I have no idea how to use it.

If you don't fix the mac version, can you at least write a step-by-step guide for mac people explaining how to set up the source version?

add the ability to dump market data to a space or comma delimited text file (or excel). this would allow me to calculate market statistics and other calculations with the market data.

be able to tag a trade to remove it from your list + let others know it is a scam(ie: need to sell 36 of said tag to get that trade buyers price)

and overall, bold the ammount if the buyers order requires more then 1 of item as minimum quality

I wrote this article on using EVE Central to haul profitably. Note that this points out that EVE Central does not include the effect of the 1% universal sales tax. This would be a nice automatic feature to add, as an option!

I frequently use Eve Central to find the lowest regional price for an item so I can put my item on the market under the lowest. Why not add a filter so when the user searches in multiple regions, it only shows the lowest sell values so we don't have to hunt through the listings anymore.