"Merging" country

Hi all,

so, it seems that the PC I’m using to render Europe’s maps does not have enough power for this job and I cannot create some help tables I need to display the city boundaries. Maybe later I’ll have other problems too, so I must find another solution…
Buying a better PC is not an option, since the maps are for a opensource project, distributed as free, so I cannot buy an expensive PC for a project where I’ll not get a single Cent…

I already rendered single countries on a test VM and it works, so maybe I can import one country, render it, export the data, drop/rename the DB and start with the next country…

The problem is, that I don’t just want to have the data in a SQLite-DB for using with OSMDroid, but I need to export the rendered tiles on a web server to use them in another application.
Currently I just rsynced /var/lib/mod_tile/ to the webserver and it works, but what happens if I want to “add another country”? Is it possible at all? How? Just adding the new files?
Or maybe mod_tiles works different and I can just add the tiles from a new DB without any changes (just not deleting the old files)?

Maybe I can use another way and use the SQLite-DBs on the web server as source for the tiles, like the App on Android.
Does exist an application (PHP, PERL, Java if no other possibilty) to get the tiles form the SQLite and serving them on the web?

Thanks a lot for your suggestions!