The Germans were tricked into making the 8.3" armed Blucher armoured cruiser when they should have been making Nassau to counter the British Invincible class battlecruisers.
Could the German navy's five most modern armoured cruisers (Blucher, Scharnhorst-class, Roon-class), have been updated to stand in battle against Invincible and the RN's other 12" armed battlecruisers? Tearing them down and changing to turbines or more powerful machinery is not likely an option due to the time and expense - might as well focus on building more Nassau class.
So, to start with, we'd need to increase their firepower. Per
http://www.navweaps.com/ Blucher's 21 cm/45 (8.27") and the four earlier 21 cm/40 (8.27") guns fired a 238 lb projectile, vs. the Invincible's 12"/45 firing 850 lb projectiles. Can we replace the 8.27" guns with fewer of the 9.45" gun (474 lb projectile) from Austria,
http://www.navweaps.com/Weapons/WNAust_945-45.htm
The complete twin gun Austrian turret weighed 235 tons, vs. Blucher's twin gun 8.27" turret at 197 tons. The twins on the Roon and Scharnhorst class weighted 171 tons.
Roon-class
Scharnhorst-class
Blucher
As a comparison, here is the earlier Austrian 9.4" gun in the KuK cruiser Erzherzog Ferdinand.
