Most of the Volvo engines sold today are attached to IPS so no practical ability to switch brands of engines. I would also add this. While I've heard a lot of criticism of Volvo over the years, I really haven't heard much on recent years of production. This situation does surprise me. When it came to gas engines on boats on the lake, Volvo had developed as good if not better reputation than Mercruiser. In fact, the general view was better engine but more expensive to repair. In terms of diesel, I see very little Volvo being installed today, other than IPS. The few builders I see using non-IPS Volvo appear to be builders who also use a lot of IPS.
If you get a new engine to replace the one giving problems, properly installed, and with a full new engine warranty, then be very thankful. Don't get greedy beyond and do not threaten at any point involving attorney's or suing. The moment litigation enters the picture, then they turn it over to their legal staff and any agreed solution may be out the window.
Now, when I say I believe they know the problem, I look at that as good in this situation. It means they also know the engines involved, have corrected current models, and know how not to repeat it.