That is a tricky question indeed, just like pulling at a loose thread. It comes down to how far do you want to go, tidy it up just to ensure it's reliable for the short term, and if it's in reasonable shape live with it, or pull it down, get it lip cut and honed, new bearings rings, seals, gaskets, timing chain etc etc and your'e well into a new build, If as you say it may not be permanent, why put good money into it..,
If you have access to measuring tools, it would tell you a lot just how much wear you have below the lip.
FWIW, I had recently had my block machined for a complete rebuild, it too had lips on all the cylinders didn't seem to large but on measuring they had worn on average 20-27 thou. It had been to the moon.....,