or stack small item like 5 jackets and 10 rings 10 necklaces 5 helmets ect just make some manageable system if you want people to buy backpack spots be careful some games I have played made the inventory so small you couldn't do missions with the basic inventory but for organization sake stack Items please!!! plus you have a selling platform for multiple Items already lol
Also, if you want to increase the relevance of the backpack while making things convenient for the gamer and not look like a greedy bastard, just put in a but load of different crappy gear for lvl 1, lvl 5, lvl 10, etc, full range of diff stat gains and make them more common on lower lvl's, that way a player will have a major desire for the backpack (storage expansion) early on because they don't want to miss out on phat loot.
Example, say lvl 1 gear gets 1 stat upgrade total and some rare special items, set or blue quality and whatnot that goes a little further, you all ready have accessories for +1 stats in the store but lets say if we gave helmets 2 stats they can focus on instead of just charisma, say financier, then you have 2 basic lvl 1 helmets that can float in a players inventory, and a weapon could boost tactics solely or ingenuity (increasing ship build rates) giving 2 diff lvl 1 weapons. At lvl 5 gear could boost 2 points in 1 stat or 1 point in 2 stats, so your accessories for a lvl 5 player to loot just went out the wall without considering set and rare drops and in addition to armor and weapons giving +2 to single stats they can do +1 to 2 diff stats and do ful range of +1 tactics and +1 any other stat or +1 ingenuity +1 any other stat on the weapon as an example while keeping an emphasis on 2 relevant stats, at lvl 10 you can start introducing items that give bonus's to 3 stats and you get the idea. You keep a base amount of stats total an item can give for a certain level so it is all balanced. And at the end of all this work, and I know at the beginning doing this and making pictures for each one might be a nightmare, but you end up creating the diablo loot effect (players wasting hours in search of loot and going nuts over every new item) making the game more addictive and you make the gamer want to buy a butt load of backpacks as they will have numerous commanders at various lvl's, throw in people being able to sell them on the trade platform and you will rake in the dough on backpacks alone while making the game more enjoyable to the players, but if you take that strategy and don't make items stack able players will quickly get into the habit of simply selling any item deemed unnecessary and forgo multiple backpacks for a more practical outlook on loot. Think on it, why do whats been done when you can do better?
only other games I played like star supremacy is evony and galaxy online, please be careful about copying either games market strategy too closely as getting too greedy, especially early on, will bite you in the rear. Marketing people buy a backpack so they don't have to keep selling multiples of the same item suggests putting greed before the gamers convenience, market wise and customer relation wise I believe it would be more beneficial to make items stack able. I personally plan on showing financial support (not a whole lot, not a rich man) when the game goes live if it is reasonably priced, while I understand the strain and need for the game to become profitable quickly, if you try to take too much from individual gamers you will lose out in the end. A good market strategy would be to allow cash shop items to be sold on the trade platform for gold or resources (allowing a player to choose what form he wants his payment in (wheat, ore, etc.) will make this 10 times more successful) that will encourage players with plenty of money lying around to spend on the game while balancing the advantages of the cash shop so hardcore cheapskates can still get the same advantages as paying players, in my experience this has been the most successful market strategy in any cash shop on free to play games. Got a little off topic, but my main point is to all ways try to keep gamers convenience in mind when it comes to marketing, and galaxy onlines greed killed that game for me, no chance in hell I will blow $50 a month on a browser game, $5 I will do, and I appreciate the work put into making these games and making them available to the masses. Just my 2 cents