well.....
this time area is not my expertise, but wasn't the biggest problem with battlecruisers the fact that they were used in the battle line? a ship with similar qualifications but smaller guns would still be capable as a scout cruiser, the falklands battle would be the same, but they would not have been sacrificed at jutland...... while they would not have been omnipotent ships, neither were the battlecruisers.
also, wasn't the dreadnought a fast BB when build
I don't think we are not really talking about a scout cruiser, anything with 9.2+ guns will be expensive and used as the main force of any fast taskforce, the problem is that you end up with a ship that still risks Jutland re HMS_Black Prince and cant fight other BCs, SMS Blücher.
http://en.wikipedia.org/wiki/HMS_Black_Prince_(1904) and
http://en.wikipedia.org/wiki/SMS_Bl%C3%BCcher
Not sure that Falklands would be the same (I think its harder for the RN but they may still win) and they might still die if they go to Jutland.
Yes Dreadnought was faster than PDs.
I think all 1/2 measures are bad value, but if you have paid for the guns already you might be worth it...
JSB