There actually are a few maps with meets your requirements, all three by [{CZ-SK} Vondy](
http://warlight.net/Profile.aspx?p=999227065):
- [Czech republic - small](
http://warlight.net/Map.aspx?ID=4791)
- [Slovakia - small](
http://warlight.net/Map.aspx?ID=4800)
- [Czechoslovakia - small](
http://warlight.net/Map.aspx?ID=4801)
Also, there's "[Duel](
http://warlight.net/Map.aspx?ID=215)", "[Truel](
http://warlight.net/Map.aspx?ID=4985)" and "[Quadruel](
http://warlight.net/Map.aspx?ID=4989)", but those are probably too small for your testing.
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I cannot proof, but have a very distinct suspicion, the AI ignores bonuses with a negative value. Not "ignore" as in "doesn't try to conquer", but as in "entirely oblivious to the fact it should NOT try to conquer them".
What *might* work (for now, it's extremely likely to break if/when Fizzer gets around to updating the AI) is to make a map specifically for this purpose. You'd give every territory (or small cluster of territories) **two** bonuses, which exactly coincide; they consist of exactly the same territories. Then you give one of those bonuses +1000 and the other -1000.