That's a reason it sucks to OWE debt with a deflationary currency not a reason you don't want to be OWED debt. But it comes out in the wash.
In the current world, currency inflating by 1.2% (someone quoted this from bureau of labor and statistics but it might as well be X for this example). Banks have to increase the interest rates they attach to loans by this amount so that they aren't losing money. For example, $100 loaned for 1 year would only have the buying power of $98.80 so I'd have to charge 1.2% interest just to break even and get paid back $101.20 + markup interest.
In another world, currency deflates by 1.2%. In this world banks simply charge markup interest because the money they are paid back will be worth more than the money they loaned. So, the same $100 loaned for 1 year would have the buying power of $101.20 + markup interest when paid back.
Either way the person taking loan has to come up with 101.2% of the borrowed amount of purchasing power plus markup interest. The only real difference is that in the deflationary world the lender doesn't have to try to measure, predict, and include the rate of deflate/inflate in to the interest.
"Say you loan me 25 bc. Let us assume I earn 1 bitcoins per week, and that amount will buy 5 MacBook Pros. At the end of six months, that amount will buy 10 MacBook Pros, and I am earning only 0.5 btc per week."
That's some pretty extreme deflation let's go with a more realistic and still high rate say 10%. Let's make it a year. So I loan you 25BTC for 10% interest so you have to pay back 27.5 BTC. Let's say you selling MacBook Pros and currently sell 5 MacBook Pros a week (0.50 BTC cost and 0.20 BTC profit each, so .70 BTC to consumer) and earn 1 BTC a week. By the end of the year (I'm going to ignore amortization because it doesn't change the concept and I don't want to bother calculating it). At the end of the year your MacBook Pros would be sold for .63 BTC, cost .45 BTC and net .18 BTC profit each. So yes, you'd need to increase your sales to pay back the loan but your potential customers salaries would be worth 10% more year on year so they could afford to buy 10% more of your product. The result of this is that deflation means 10% more goods/services would need to be produced to cover deflation. Just like 10% inflation would mean 10% more goods and services would mean the same.
Unless you are talking about a salary of say 1 BTC a week. It isn't like an employer would be able to cut salaries for deflation, they also wouldn't need to increase salaries to offset inflation like they do now, merely for merit. So you'd still make at least 1 BTC a week, it would just buy 10% more goods and services. That works out because your company and everyone elses increased production by at least 10% to cover salaries and pay back debts. That was easy for them to do because their goods and services are flying off the shelf 10% faster because their clients have 10% more to spend on their goods/services and their costs dropped by 10%.