Greetings fellow Warwick aficionado.
I have the same idea as you (running lots of CDR), but I go about gaining my CDR in a slightly different manner. I run 1 Flat CDR Quint, Full flat CDR Blues, 5 Flat Armor Yellows, 4 Scaling Armor Yellows, 2 AtkSpd Quints and 9 Hybrid Pen marks. I also go 21/9 Offense and take 4 points in the cooldown talent. This gives me 15% CDR from the jump. I then focus on getting Lucidity boots after L6, and a kindlegem (to slot into Spirit Visage eventually). I find this gives me a full 40% CDR at a decent speed and fairly reasonable price point. I find that WW can manage this rune setup due to his innate sustain in the jungle (thus a few scaling armor seals), his preference to remain in jungle into L6 (Penetration helps him vs. Camps and Champs) and the sheer amount of Magic Resist he likes from his items (Wit's End works well with his passive, ult and Q, while Spirit Visage turns him into a self healing drain tank).
My build order is blue knife (so I have 1 slow for counterganking and running down the enemy team), devourer crystal, followed by either BotRK or Wit's End depending on enemy team (if enemy team is tanky, slippery or top bruiser/tank is strong, go BotRK first, vs strong midlaner or lots of AP go Wits) for the damage, stopping to grab Lucid Boots and Kindlegem when I hit L6.
After grabbing Devourer, Lucid Boots, Kindlegem and choosing to grab BotRK or Wit's End, I pick up a Warden's Mail, finishing the Randuins Omen if I have Wit's End, or picking up a Specter's Cowl if I went BotRK first (to balance out my resistances). Following this, I'll look to complete the other damage item that I didn't choose earlier, as well as finish the Randuin's and Spirit Visage. Final 3 item build order varies by match.
Finally, if you are at a point where you absolutely know that the next fight will be your last (70 second death timers), sell boots for Ninja or Merc Treads and drop Spirit Visage or Randuins for Guardian Angel (being able to come back and Q someone for health+buff team with W one final time can sometimes win a game). As WW, you want to ult lone targets - the solo laners in laning phase, or pickoff targets who wander out by themselves, or, if heading bot lane (or at any duo), pick the champ that has the most CC (like, if enemy lane is Graves and Janna, ult the Janna. You'll kill her, push Graves out, take a dragon or at least apply a lot of pressure bot. If you Ult the adc, Janna just bounces you out. If vs Thresh and Trist, tell your botlane to track Trist ulti and gank solo laners until Trist lacks knocbck). In team fights you are not the primary engage. Be patient and wait for the enemy to blow some CC on whatever teammate engages or wanders haphazardly into a fight (aka, the nunu engage), thus increasing your odds of getting off a clean ult w/o getting knocked out. Don't think of yourself as an engage tank, but an Assassin who becomes a life-stealing bruiser after picking off one of the damage threats. Targets with Merc Scimitar should be avoided, thus WW can sometimes suffer vs. AD mid comps, as the mid and adc can both fit an early QSS into their kit no problem. Always ult the Kayle, never ult the Azir who hasnt ultied first or the Jax with swirling things around him. Sometimes killing the support is the best thing to do (kill that Janna repeatedly).
Also, Ive mentioned Randuins a bit. I find it's a lot better for WW than Frozen Heart or Thornmail. Without the Randuins, you lose out on 500 HP, and the above WW build you only have 1 HP item aside from it - the spirit visage. Without Randuins you struggle to break 2k HP, meaning you're trading 30 more armor + effects you either don't need or can't optimally utilize, and a ton of MR but not a lot of health. In my setup, the CDR from Frozen Heart is not needed, and you get a similar attack speed debuff from Randuins as you would from FH as soon as the enemy attacks you. (You jumped on their face, someone will attack you) Thornmail in this setup doesn't have enough HP or Armor (you're getting 1 armor item total + runes), making you a 1700 end game HP wolf which isn't enough for a melee unit with no escape. Randuin's also gives Warwick the same advantageous functional utility that blue smite does: A slow. Warwicks ult is his only CC. Blue smite can help WW slow other targets prior to L6 for his laners to catch, and Randuins Omen allows Warwick a small escape/engage slow, or superior cleanup potential. When the enemy is half dead, WW's "E" gives him a massive movespeed bonus, coupled with Randuins Omen allowing you to now catch up to the a wounded enemy and any nearby friends and slow them all. In the same way Righteous Glory starts a fight, Warwick with Randuins Omen finishes it.
I hope this gives other people some ideas. Warwick is a great beginning jungler and Ive found he sticks with you, always remaining a fun champion to play. Although not mechanically complex, he requires discipline and game knowledge to shine. As WW, you must have the patience to wait for the correct opening to Ult, you must know when to hide your "E" (as having it always on can tip the enemy as to your location), and you must learn to play around your "W" and "Q" cooldowns just as much as your Ultimate (you can only sustain yourself in a fight when those abilities are available, so you'll have to find your skirmishing rhythm for yourself, knowing when to weave out of combat and drop aggro, when to tank damage for your team, etc.), not waste your item snares on corpses that haven't fallen down yet while still making certain that deaths are secured; and perhaps most importantly, after giving up early aggression (you can still have presence as a farm jungler via wards, counter ganks and attempting to track/mirror the enemy jungler), you must always be thinking about how to turn your first 3 ganks (about a 300ish second window after hitting L6) into gamebreakers.