I don't believe this is possible; we've been investigating similar things. At its core, the problem lies in the fact that pricing rules are triggered in the basket.
Therefore; if nothing is added, the pricing rule cannot trigger. The behaviour you're describing (price type becoming available before things are added to the basket - and the customers being able to choose that price type or not depending on their circumstances) is best suited to an offer. But then, of course, it's not Constituency-driven.
Please, hive mind, feel free to contradict me if I've fundamentally misunderstood things, but I've been trying something similar before now with no joy.
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X.