And this is where it would get interesting. There would now be a clear financial incentive for the borrower to repay the ISK + interest and the lender would be well protected (essentially via an over collateralized loan).
Therefore, unless the lender does not mess up with their collateral requirements they will not lose ISK.
The borrower, if unable to pay, would though lose their items and they would be sold by the lender to (hopefully) buy orders in the market. Using the above example essentially 1.3bn ISK of items are now longer available to the borrower to use as new collateral to get new loans + 1.3bn of buy orders have gone and so presumably those prices have fallen + therefore there is not a requirement to manufacture those 1.3bn of items. In all, the Eve economy has shrunk due to this borrower defaulting which leads to an effective ISK sink . . . . . though admittedly in the beginning it will really be items not in use being re-circulated into the Eve market - but this would allow corporations to put those dead assets in play to allow them to borrow funds to wage war!
Worth noting, that the appearance of this mechanic in the game would create much more than just the ability to issue loans. It would also allow the appearance of forward trades (i.e. derivatives).
Lets say that you wanted to buy 1bn of Tritanium at todays prices, paying in 1 months time for your manufacturing schedule but you feared the price was going to go up by 10%. And lets say that I took the view that the price of Tritanium was going to be flat or be lower in 1 months time.
Hence, as we stand today i would be happy to deliver to you the Tritanium in a months time for 1bn ISK at todays prices. . . . . i believe i would make a profit and you would feel you saved from buying at a higher price.
And lets also say that you were willing to pay 20m ISK now to guarantee paying that price for the Tritanium (i.e. you pay 2% of the buy price = 1.02bn ISK in total).
Using the above mechanics:
Step 1 - the first item exchange contact would be for you to pay me 20m ISK and for me to exchange 300m ISK of items.
Step 2 - the second time based contract (but issued at the same time) would be in a months time you paying me 1bn ISK (so 1.02bn ISK in total) and the 300m ISK of items returned for me exchanging with you the 1bn worth of Tritanium at day 1 prices.
(If i break the second time based contract you get 300m ISK of items for 20m ISK which will cover the rise in the price of the Titanium.)
So, if the price has indeed gone up by say 15% you will have saved 13% (15% price rise less the 2% cost of this contract). If the price has fallen by 5% then i will have gained 7% (5% less cost to buy the tritanium + the 2% fee paid to me).
Of course, if the price is more than 30% higher then i will not pay the second part of the contract and so lose the 300m ISK of items and we both lose but you are least are 280m (300 - 20) better off.