Parfait is very, very good in the nordic meta, even though it is only rarely played. Nether Void prison haven't really showed its power yet, but i think that it has potential (in particular if Mana Vault is unrestricted). As an example of a working prison deck, this one won the 34-person n00bcon 4 tournament (before restriction of mana drain even though the deck only plays one, and with current errata on winter orb, i.e. it still works while tapped):

ENCHANTMENTS (2)
1 Underworld Dreams
1 The Abyss

SORCERIES (6)
1 Braingeyser
1 Time Walk
1 Recall
1 Balance
1 Demonic Tutor
1 Mind Twist

INSTANTS (10)
2 Divine Offering
1 Ancestral Recall
2 Disenchant
1 Mana Drain
4 Swords to Plowshares

ARTIFACTS (24)
4 Howling Mine
4 Relic Barrier
3 Icy Manipulator
1 Jade Statue
2 Winter Orb
3 Fellwar Stone
1 Black Lotus
1 Sol Ring
1 Mox Sapphire
1 Mox Emerald
1 Mox Jet
1 Mox Ruby
1 Mox Pearl    

LANDS (19)
1 Strip Mine
4 Mishra’s Factory
1 Mishra’s Workshop
4 Scrubland
2 Tundra
3 City of Brass
2 Underground Sea
1 Maze of Ith
1 Library of Alexandria

SIDEBOARD
1 Power Sink
1 Disrupting Scepter
2 Disenchant
2 Underworld Dreams
3 Wrath of God
2 Circle of Protection: Red
1 Jayemdae Tome
3 Blue Elemental Blast

The way we did it in Sweden was to start with minor tweaks, and I agree that it's a good idea. Once the community grew larger and we had some more data to work with, we tried to base our decisions on results rather than gut feeling. Here's the timelime for our B&R btw, if you're interested:

2007: Pretty much only two players in the start. After a few months, we have 4-5 more players. The first list reflected the original B/R exactly:
Restricted: Ali from Cairo, Ancestral Recall, Berserk, Black Lotus, Braingeyser, Candelabra of Tawnos, Channel, Chaos Orb, Copy Artifact, Demonic Tutor, Feldon's Cane, Ivory Tower, Library of Alexandria, Maze of Ith, Mirror Universe, Mishra's Workshop, Mox Emerald, Mox Jet, Mox Pearl, Mox Ruby, Mox Sapphire, Recall, Regrowth, Sol Ring, Time Walk, Timetwister, Sword of the Ages, Underworld Dreams
Banne: Divine Intervention, Time Vault, Ante cards

2008: First tournament is held at a convention in Gothenburg. B&R is updated pretty heavily before this. Time Vault and Divine Intervention are unbanned; Chaos Orb and Falling Star are banned; Ali from Cairo, Candelabra of Tawnos, Copy Artifact, Ivory Tower, Sword of the Ages and Underworld Dreams are unrestricted; Balance, Black Vise, Fastbond, Mana Vault and Strip Mine are restricted.

2009: Still very few players, and no changes to the list.

2010: One update in February/March before n00bcon 2:  Mirror Universe, Feldon's Cane and Berserk are unrestricted. Another update before Rotary Champs in August: Time Vault and Power Artifact are restricted.

2011: No changes.

2012: In February, Chaos Orb gets errata and is unbanned and restricted. The Swedish old school community have grown to over 60 persons, and it's not really viable to have complete consensus discussions with everyone regarding the other restrictions (although we obviously take all feedback we can get). A smaller group of organisers and players representing different ideas about the list start have discussions. After n00bcon 4 during Easter, Fastbond is unrestricted and Mirror Universe and Shahrazad are restricted. The tournaments was getting popular (34 players at n00bcon 4), we've started to have timed rounds, and hence 4-off Shahrazad is way to time consuming.

2013: After n00bcon 5, we decide to restrict Mana Drain. This lead to a lot of complaints initially, but turned out to be healthy for the format. Mana Drain had been a major bogeyman, and every single final in larger tournaments for the last years had been between two The Decks with 4-off drains. 7 of 8 decks in the n00bcon 5 top8 played multiple drains, and it was completely locking down non-control strategies.

2014: Unrestricting Mana Vault after n00bcon 6. The main idea is that it will allow combo and prison to be a little stronger, and help out budget decks. The format has grown fairly popular (tournament attendance is generally higher than for both Vintage and Legacy tournaments in Sweden), and there is only so much power in the country to go around.

Very interesting discussion! Time to dust of my old TMD account

It is possible that Mana Vault will have a big impact. From my experience in playing with it in a transmute artifact deck, I've always felt it was far worse than fellwar stone though. My guess is that it will be strongest in an O'Brien deck (which wasn't really viable before), and be a good alternative in budget decks. It will probably be played in Gauntlet of Might decks as well. Should be interesting to see what happens, and if us players of today can find a better shell for it than we could in the mid 90s.

There are some proponents over in Sweden for Black Vise and Strip Mine being unrestricted. As both card are reasonably cheap and attainable, I would not be surprised if they were to be unrestricted at some point in the format to test what it would be like for a year or so. If you decide to try out unrestricted workshops, strip mines or vises in a tournament, I'd be really interested in how it works out.