Exactly. I mean, it's a good and very interesting idea, but we have no idea what would happen! Really, any speculation on this is just not possible with any firm base in fact.
That is the problem. I have created a map for that is supposed to illustrate things, in regard for how sparse our knowledge of pre-IE languages actually is. Note that the map is ANACHRONISTIC, depicting times between circa 800BC and 50BC, depending on where on the map you are. It's also quite inaccurate, but it's supposed to be a visualization, anyways.
Also note that I used UCS colors, but I heavily misused them.
- Swedish dark blue denotes the areas where Uralic languages were spoken. Note that Estonia probably was originally Baltic-speaking, and became Uralized only later. In Antiquity, there's mentioning of a (very probably) IE-speaking people called the "Aestii" which lived along the shores of the Baltic sea, and with all likelihood, they were Baltic, and the name got later inherited by the Estonians.
- British red is the area of the Picts. As far as I understand it, there's the discussion wether Picts were non-IE, non-Celtic-IE or Celtic. In any case, there appears to have been some pre-IE residue in the Pictish language, which wasn't preserved in other Celtic languages of the British Isles.
The situation in Iberia is approximately in 200 BC:
- French blue is for Aquitanian, aka Old Basque.
- Spanish brown is for Iberian, and the lightly colored areas are those that presumably spoke Iberian previously, but were subsequently Celticized.
- The Mali dark grey area is where Turdetanian (the descendants of the Tartessian) was spoken. The lighter grey area is those where - presumably, Tartessian was also spoken earlier, however the denizens of these areas (the Turduli) were Celticized or Lusitanianized. The relationship of Tartessian to Basque and/or Iberian is unknown.
- The northern area denoted as Celtic probably was the area of Iberia first to be Celticized (around 600-500 BC).
- The Lusitanians were clearly Indo-European peoples, though there's the dispute wether they spoke a variety of Celtic, a language related with Ligurian, or an isolated IE language.
- Lighted Austrian pink denotes the area of approximately where Raetian was spoken, which is very disputed in it's affinities, as far as I understand it.
- The Italian colored area (and it's lighter variety) denotes the area where Etruscan was spoken.
- Carthaginian Pink in North Africa denotes Berber languages spoken there.
- Babylonian blue in Anatolia denotes Semitic influence (principally Aramaic, the official language of the Assyrian Empire).
So, in essence, we know virtually nothing about the Pre-IE languages in most parts of Europe.
I also think the Kurgan hypothesis has the greatest base. Obviously nothing is certain, but the Anatolian hypothesis has several major flaws, notably the lack of agricultural reconstructed vocabulary, and the fact that the most plausible dates for the time of PIE simply do not match up.
I agree, the Kurgan hypothesis is probably the one that works the best.