Step one: create a bathroom escape

We meet with the detailed planning team next week, but because we are renovating both bathrooms and the kitchen, which are all connected by space and plumbing, I fear that we will have spells of time during the six months of renovation when we will be toilet challenged. At one point, a previous owner had placed a powder room in the basement with what looks like a mascerating toilet based on what is left. A current neighbor who grew up here suggested it was about in the 1990s. For some reason, that strategy failed or at least abandoned so the space was a storage area for storm windows, unused doors (with “Rockne” logos), etc. Here is what it looks like in all its “glory” today:

That window will be gone during the renovation and be underneath the new kitchen sink. What that means is that anything we do in this room even temporarily will not at all be something that might be useful in the future. But I am very worried about having adequate toilet and washing areas, so we’re thinking about renovating this to the minimum degree to give us at least temporary options. We, theoretically, can easily add a mascerating toilet and a sink that is useful. We can clean up the crap and add some teak floor boards to make walking palatable. Ideas while we wait for a plumber to consult?