The water pump will eventually fail and seize up. If the engine is ran after that it will over heat and likely require expensive repairs. There is also risk of water pump derbies getting stuck in hard to clean places.
Usually you will hear noise coming from the pump before complete failure, but I would not count on that as a warning sign.
Ebay seems to have a number of Subaru SVX water pumps listed, for example:
https://www.ebay.com/itm/225212447283
I don't know if that is a good seller or not, or if they are correctly describing the item for sale.
But the bottom line: Don't skip the water pump.