Apple doesn't offer warranty replacement Macs during service unless you are paying / participating in the Joint Venture program. It's basically premium service that you pay for as an add-on similar to how AppleCare is an add on that can reduce your repair costs in some cases. I don't know how many countries it is offered, so contact your store's Business team to check. From the USA web site, the program has this as one of it's benefits:
Premium access to Apple Support.
You’ll get your own website with easy access to every service we offer
— custom training, Genius Bar reservations, tech support, and
workshops. And you can speak by phone to an Apple Genius who can help
resolve your issue, check into necessary parts, and estimate repair
turnaround time. We’ll even loan you a computer while yours is being
repaired. If you prefer to meet in person, you can make a Genius Bar
appointment at any Apple Store in the world.
You'll need to rent a replacement elsewhere before you turn in your computer or time the repair to when you can afford to lose the days it takes to do the work on it.