would people like swiftness I, 20% faster, for 8 minutes or swiftness II, 40% faster, for 90 seconds? (nether roads) for the overworld, i think swift I with item dispenser would be good. for the nether, swiftness II with splash dispenser. materials: 64 redstone can get around 2 weeks of swiftness I, so that shouldn't be a problem i'd need 64 gunpowder for a lot less swiftness II, however. also, if it is thrown, you might not get the whole 90 seconds, however it takes less than 90 seconds to travel from desertopia to kaeshar (untested).
was going to say more, forgot