This is a tough one.
Here's the thing. It's a little iffy but I think it works to shoehorn the rules into the spirit of what Space Hulks are supposed to be:
The Space Hulk has a Speed value (10cm) just like other ships. However, this speed value does not matter, thanks to the special rule. Because the special rule clearly states "no more, no less" you MUST move exactly 10cm straight ahead, regardless of any speed modifiers caused. So...
1. The Evil Sunz Warboss increases the speed of the Hulk from 10cm to 15cm, but you still must move it 10cm, no more no less.
2. Soopa Boostas, likewise, add +5cm speed which is ignored due to the special movement rule. On Pg 27 of the 2010 Compendium FAQ, it states that Space Hulks can use All Ahead Full, but gain no extra movement (in order to ram something 10cm or less away). In this case, the Soopa Boostas increase the normal 2D6 to 4D6 which are still not used and the Hulk goes 10cm anyway.
3. Just as with the Evil Sunz warboss above, the Red Paint refit from Engine Refits doesn't work. (a generous campaign manager would let you re-roll this) However, according to my above logic, the Extra Armour Plating from the Ship Refits table would increase the HP of the ship by 25% (MAKING IT A WHOPPING 50 HP!) but reduce the speed by 5cm, which would then be ignored! EVEN BETTER! Under the Ork Clanz list, a Warboss that changes the Gubbins of his ships at least twice before the first Refit is earned gets the Refit FREE, INSTEAD OF INCREASING THE SHIP'S POINTS COST BY +10%!!!!!!! This means that if you play an Ork fleet in a campaign, take a Space Hulk, change your Gubbin refits at least twice, and then earn your first refit for the Space Hulk (hard, unless you have enough Renown to make multiple appeals), the Space Hulk would gain 10HP ABSOLUTELY FREE!
Hold on, I need new pants.