modding new improvement limits?

Yes.

This is an example of turning the empire archivist into infinitely repeatable

and this is an example of turning the number of repeatable buildings you can build in the capital city of empires, at level 2 only, into 4 instead of 2.

Thanks so much Heavenfall!

Now I can make a quick little economy mod.

Interesting! How does the system determine the capital?  Is it just the first city built? The one with the palace?  What if the original capital is captured or razed? You've roused my interest, as I don't remember any sort of capital marker / indicator / differentiation. Maybe it's just been too long since I've played...

The only distinction in 1.3 is a bug in kingdom capital vs following cities, the kingdom capital city starts with 50 open tiles and the following cities don't. The capital city is the first one you found. If you lose your first city and you have no other cities, the capital city may be rebuilt. Otherwise the capital city title is transferred to your next town on the towns list, but it does not change the town in any way even if you mod capital cities to be different from normal cities.

For modders it is important to note that the capital city improvementtype remains a capital city for the rest of the game, so if you mod in benefits to a capital city only it will never go away (unless the city is razed by you or AI).

Thanks:-)  Btw, was there any graphical marker to indicate the special-ness of the capital?  Because I'm still drawing a blank.

In the UI you can see what city is the capital city in the ledger for the city. http://snag.gy/OuKZy.jpg (this only appears for cities that are built capital cities, not cities that become capital cities from transfers)

If you mean the graphical representation of the city, then no, it looks the same. It could look different in a mod.

Aha.  Thanks, Heavenfall:-)  Hopefully they'll call that out better in FE.