staying in Iceland for long?
I've spent quite a bit of time there, yes.
From your reply i understand that even though winter has its moments, it is not the best of ideas to make a trip there in December
that's not what I wrote, only that as a tourist, you have fewer tours available and long distance driving (say, from Reykjavík to Akureyri) is considerably more difficult. However it's not nearly as cold as it is here. The winters are generally mild by comparison but are considerably more precipitous.
Maps aren't great, driving is limited, not even the "highway", an undivided two-lane road which rings the country is fully paved, you can't go inland without a Super Jeep, and you'll see relatively little. Many of the tours are well worth the money, highly recommended for a start (like the Golden Circle). Driving can be difficult even in summer. If you insist on doing it make sure you have a day or two's worth of easy-to-open, non-perishable food and beverage (and toilet paper or tissues) with you just in case. It's easy to get lost.
I have no idea what you mean by "confined country". It's a huge island with few people, 99% of whom live within 40km of a coast. Inland is uninhabitable with its glaciers and volcanoes. If you're into hiking and trekking it's ideal as long as you have rain gear and lots of socks. You'll definitely need a bed mat of some sort since the island is volcanic and in many places, the only thing on top of the lava is a millimeter's growth of lichen. Exploring waterfalls unguided is a good idea if you've gotten tired of that nasty oxygen habit.
There is only very limited public transportation outside the capital
Hah! There's very limited public transport <i>inside</i> the capital as well. The <i>Stræto</i> (city bus lines) don't run often, and less so in the off-season.
You're right about the Southwest. That section is called "Reykjanesbær", a conglomeration of the smaller towns (including Keflavík) which comingled a few years ago. Very big with hikers, but not a lot to see outside of nature.
There's also the national bus some of which which travel around the country (both into and avoiding the West Fjords in the northwest) and some which just run between certain cities. The tickets aren't that expensive (there are special tourist tickets which let you hop off one and onto the next one a day or two later as many times as you want for 1-2 weeks), but travel is slow and most lines run only once or twice a day.
woof.