Force of nature was a great item. And i was very sad to see it removed in season 3 and i know it has fallen out of the meta but i was thinking and i thought how you could possibly change it around to be a viable item again. so here are the possible statistics:

+25 hp regen per 5
+8 movment speed
+73 magic resist
+15 cooldown reduction
+250 health

Unique Passive: +2 hp regen per level
Unique Passive: increases healing and regeneration effects by 28%

Builds from: Spirit Visage, Null Magic Mantle, Rejuvenation Bead

Item Cost: 1030g
Total Cost: 3800g

So, basicly what it would do if it was in the game is that it would give you a late game, upgrade to spirit visage, and cost efficient hp regeneration for champions that need it for example: the high magic resist and enhanced healing would be great on Morgana and Vlad. Or tanky junglers that benefit from movement speed and regeneration ie Hecarim, Trundle, and Volibear. I do not think that im the only one out there who misses Force Of Nature, so if you wish it were back in the game please give feedback and support.

I think FoN is a tricky thing. I don't feel we really need it back, but I do think we need a new big MR item to replace it. AD and AP both got cheaper in season 3, while defenses got more expensive. This may just be Riot seeing things that we don't and trying to keep the game from getting stagnant, but sometimes you HAVE to be able to get those defenses. You could have a complete noob in mid that feeds the enemy Karthus. If you're say, the adc you don't really have a whole lot of room for defensive items, but you have to have something to survive if Karthus should ult at the right time.
Your options that you can work into your build are:
Guardian Angel +30 magic resistance: you can't get it early as it's kind of expensive, but it's not an uncommon buy for an adc.
Hexdrinker/Maw of Malmortius +25/36 magic resistance: a personal favorite of mine, it combos quite nicely with Life steal; it's not the best option but reasonable.
Mercurial Scimitar +45 magic resistance: not spectacular for ranged and situational depending on the other team's cc.
Spirit Visage +50 magic resistance: okay pretty bad if an adc has to buy this at least if buffs up your life steal. Mostly noted because it is currently the highest magic resist item in the game.
Banshee's Veil +45 magic resistance: can save your life, I had to build one against a fed Brand at one point, gave my team the win (I was playing as Ashe).

Armor is currently much easier to build than magic resistance.

Tanks don't need a super-high MR item while health stacking and MR are still double counters to most mages.

(Due to their damage being tied to cool-downs.)

Stacking HP to counter AD is a big mistake, they will vamp their whole healthpool back in matter of seconds

I honestly want a huge regen item with bonus movespeed on it. Running around with it giving you 8-10 health per second, extra movespeed the lower health you are.

i always really liked this item it was great on a champ like cho , Singed . heck i would have used it on any champ , it really was a good item . movement speed a ton of health regeneration and magic resist . it was a little $$ compared to some other items but it was worth it . meta bs ...... i would defend any person that used it .