ING argues that the pound should see less pronounced gains on a market-friendly outcome vs more meaningful losses on a non-market friendly outcome

ING UK election

The firm says that their short-term financial fair value model suggests a more than 2% positive Brexit resolution premium currently priced into the pound and that points to an asymmetric reaction in the currency after the election.

"Given the anticipated market-friendly outcome, the GBP price action is likely to be asymmetric (skewed towards more meaningful sterling weakness vs strength, as the non-market friendly outcome doesn't appear to be investors' base case)."

They also outline their scenario analysis on the pound based on the latest events and market expectations as per the above (⬆️). Here's a snippet of the commentary on that:

Thin Conservative majority
A smaller Conservative majority would initially lead to GBP gains, too (to 0.83), yet the scale of GBP strength is likely to be marginally more limited. While the Withdrawal Agreement would very likely be passed by the end-January 2020, the question of a hard Brexit might return around mid-year if eurosceptics in the European Research Group oppose an extension to the transition period beyond the end of 2020 (which would, in turn, suggest there is no Conservative Party majority for an extension). Still, as this is an issue for 2020, it is unlikely to prevent initial GBP gains.

The full report is well worth reading and can be found here.