Wouldn't it be better if lost coins were reintroduced into the network after a fixed span of inactivity?
I suppose the first thing one would say no for, would be by virtue of bitcoin's well-known deflationary property. This said, I believe it is much more important, especially in the longest term, that bitcoin keeps its property of conservation of energy, that is, having a fixed quantity of money ever available. By losing coins, instead, and by having them unrecoverable, we have not a fixed quantity of money available, rather a decreasing one, which is why we call bitcoin deflationary.
What would happen if we would make so that coins with 131 years of inactivity would be reintroduced into the network?
Bitcoin code was not written in a way that it could mint new coins, so even if your idea is good, it is absolutely not implementable, the current bitcoin code cant be uttered or changed from what and how Satoshi have designed it to operate, any one that tried to utter the code will trigger a hardfork which would lead to the creation of a new coin, which would be utterly different from bitcoin.
Do your research, you would discover that there are lots of bitcoin Hardforked coins in the market, this hardforked coins were created to correct some supposed flaws bitcoin had, but still, non of this coins has been able to outshine bitcoin even as perfect as they claim to be.