I think that's a good idea. While I agree that for me 45 IBU or so is about the perfect amount unless I'm specifically looking for a hop-bomb beer, the type of beer is a huge thing. In a beer like the one you're making 40 IBU might be just the perfect amount to balance it without seeming bitter.
A 45 IBU dry lager would be too bitter possibly, but a 45 IBU "big beer" like an imperial anything, or baltic porter etc, would be "barely any hops".
Rogue makes a chocolate stout I really like which is 69 IBUs, but it's just barely pushing the bitterness threshold of "too much". In a regular beer that would be "very bitter" but in this case it just works.
I've also had an Imperial IPA that claimed to be over 50 IBUs, but I could barely taste the hops it was so sickly sweet!
This is exactly what I mean: hop bitterness perception in beers, like acid perception in wine, depends entirely on everything else that is there. A fresh dry 5% abv ale or lager with 50 IBUs would be rather bitter to extremely bitter depending on your tastes. An Imperial Stout that is 12 months old with 12% abv and a FG of 1.025 with 50 IBUs will be so sweet you won't know there are hops there at all. Imperial Stouts are highly hopped to combat the "this beer tastes like sugar" effect you get in a lot of "winter warmer" type beers: dark, high abv, long aging times, very high FG. You can lower the hopping rate, no problem, but it will be closer to a different style: barleywine, old ale, etc and not an Imperial Stout. Obviously this is all semantics and you can call it whatever you want and use any ingredients you want. If you have the space, try making a small batch with twice the hops and compare them 18 months from now.
If you're in the mood for an experiment, I would suggest seeing if you can find Pliny the Elder (Russian River), 90 min IPA (Dogfish), or any other DIPA [although so far these two are the best IMO]. Buy two bottles, put one in a cool dark place. Drink the other one right away (holy bitterness!). Drink the one you saved 6 months later (and if you bought Pliny, ask for forgiveness for aging it) and compare the flavor. What a difference time makes. I can drink about 2 oz of fresh Pliny before I am all bittered out. A 3 month old bottle is awesome; although it is still extremely bitter, the harshness is gone.
Edit: more posts while I type! Ack!
Yes, CG is right about the acclimated starter of EC-1118. Just adding it to a finished beer is a recipe for a finished beer with a yeasty flavor. Getting it going (in a wort or honey must, whatever you like) and then slowly adding the beer into it will get it used to its new home and get it to its full potential.
Don't worry about this going dry, you'll have lots of residual malt sugars in there. Since you're "diluting" it with honey, I'd suggest doing a longer boil to promote some extra long-chain sugars, which are formed during the boil. 90 minute boils are common for huge beers like this (keep track of volume loss due to evaporation).
Hop utilization does change with time. There are lots of online calculators out there. Here's one from
Tinseth. I often use the calculator at Beertools.com. Each calculator comes out with slightly different numbers, and they are all just estimates. [this leads into my "112 IBU on paper" comment: the real IBU if tested in a lab was surely no higher than 80.] You can play around with the %AA and times to see what effects you'll get from using different hops for different times.
Adding hops after fermentation (dry hopping) will add aroma without any bitterness [adding bitterness requires boiling to isomerize the acid into a water soluble form]. Aroma is pretty fragile, however, so if you wanted to dry hop I'd do it right before bottling. Any earlier and it will just age out. Bitterness really, really ages out and changes character over time.