Build a Website with magento

First one > In FF every item has percentage markup value added to all products. If a vendor loads a product and lists it for sale say for $100 the buyer (consumer) will see the price as $120.00 since we set the markup as 20%. The extra function would be as a range, for example, all items for $20 below will be a 30% markup, and everything between $20 and $250 will be 25% markup added to the list price and all over $250 will add 20% markup to the purchase price. The percentages are for sale. Point -2 the client requested the ability to build "lots." For instance, a vendor would be able to choose a number of items produce a "lot" and sell the whole "lot" as one item or SKU with multiple product SKU's Point -3 and the a new mod will be installed the RMA Return Merchandise Auth which this is what we need as customization