I would be happy if I could track my Gizmondo games.

Sure they are low in numbers, but if the N-Gage and Pokémon Mini gets one, Gizmondo should get one too! 
 

Many collector's editions of games include a steelbook case as a limited or exclusive item that is heavily traded and sold in the aftermarket on eBay and personal ads. I believe many of them have a significant value that can add another layer to the item checkboxes for included items (such as box only, manual only, loose items, etc). It could also be included in a separate section like the Figures tab as well. I have many of these cases myself and would love to be able to have prices tracked for them and have a way to keep an updated list of the ones in my collection. Thanks for your consideration! :)

Brazil was a huge market for SEGA. The Master System and the Mega Drive were insanelly popular back in the 90s. So they got some exclusive games and this also includes some games for the SEGA CD. I believe its a mistake to ignore the game library of this south american country.

I like too see what i own and all that other stuff but not everthing is here for example i have a PAL Playstation 4 slim Gran-Turismo but it isn`t shown. So, it would be nice.

Users can add eBay Listings and then they would be put under the corresponding catergory (Loose, CIB, New, Box or Manual).

I like there to be an option to remove all the the console's in the filter list that do not have a game in your collection. That way I don't have to scroll though as many options and I can get to what I want to see quicker

Seller should be able to correct tracking information after input

Since Arcade1Up is showing signs of limited runs, as well as systems apparently being purged from Walmart for dirt cheap ($50 for new $450 machine), I think the collectors value of these machines is going to go up. As an owner of 6 of these, I'd love to be able to add them to my collection as well as track their current prices.