Developer needed to create a marketplace of virtual items using blockchain smart contracts

Although a fixed price had to be specified for this job, we want to discuss the plan with you and decide on a good price for the various deliverables. We run a platform that contains “virtual items”. They represent a potential value in the future. We need a system where people can buy these items (from us and each other). BLOCKCHAIN PLATFORM. We’re open to any suggestion. Waves, Ethereum or some other platform that you’d recommend. For convenience we assume that Ethereum will be used in the remainder of this project description. (D)APP & REQUIREMENTS NOTE. We envision to use our traditional non-distributed app that communicates with Ethereum’s blockchain for transactions and ownership of items. Below we describe the features we think should be in, but we’d like to discuss the best approach to take. CROWDFUND CAMPAIGN We start with a crowdfund campaign. People invest a certain amount of money and receive tokens in return. These tokens can be used to acquire the items. ITEMS Ownership of each item will have specific rights related to it. For example, “In possession of this item you’ll receive XYZ if ABC happens”. An item also has other attributes, like a name. SUBSCRIPTION We assume that investors need to create an Ethereum wallet first. We also need them to subscribe on our platform with a (user) name, email address, and profile image. We guess their account on our platform can be connected to their blockchain address. TOKENS Once registered, we could manually send our crowdfunding investors the amount of tokens that reflect their investment. The initial amount of tokens equals the investment (in Euros). We must be able issue more tokens over time. BUY ITEMS FROM US At one point the market will open and investors will be able to buy the items. These items have initial fixed minimum prices per type. We’ll release additional items over time. It should be possible to buy them via our website. So on our website, users select an item and set the price they’ll pay (they can pay more than the minimum price). This should trigger the transaction in Ethereum. BUY ITEMS FROM OTHER INVESTORS You are the rightful owner of the item until someone is willing to pay +10% or more than the price for which you acquired the item. This again should be possible via our website, calling Ethereum to do the transaction. The previous owner receives the initial price for which the item was acquired + 50% of the surplus. The other 50% goes to us, the owners of the platform. So, if the price was 10 tokens the previous time, and 20 tokens now, the seller receives 15 tokens and 5 tokens go to the ‘reserve’ (we don’t/can’t buy items). NOTE. Let us know if we understand blockchain / Ethereum well. Important for this to work is that such a transaction can take place invoked by the buyer only. It would be a problem if there must consent from the seller also. The concept is that an item is always sold, whether the owner wants it or not. DISPLAY ITEMS & OWNERSHIP We should be able to display all items and who owns them on our website. - Attributes of item - Owner - (Minimum) Price OPTIONALLY The following features have less priority but are important as well. Please specify a price for which you’ll develop each feature. 1. CALL DATA On the web app we should also be able to show: ALL INVESTOR DATA. user id, property ids, total value of properties, free tokens. ALL TRANSACTIONS. Seller id, buyer id, property id, price. We’ll use the info to show overviews, but also to notify users via email that someone has bought an item from them.