Generally, all miles you don't "fly" will only earn for award miles. There used (?) to be some us-american programs where you simply could shop yourself for *G lifetime if budget allowed, but afaik they changed those conditions.
You're correct about M&M resetting your status miles at the end of the year.
I assume you know how to calculate your milage earnings, and you've some idea if you'll be earning miles or not on those Y tickets (they're on SQ, right?)
I would calculate the following:
Will whatever you've left flying in 2011 be enough to make FTL? (17.800 miles)
If not, how much will it be? Yes, you could make KrisFlyer *G probably easier than SEN, but besides lounge access, it won't give you much additional benefits, especially when flying LX or LH, a cheap A3 *G would bring you exactly the same. And the redemption rates on SQ are a joke. There is a reason not many apparently choose their program, even if they got many flights on them
Only their "premium" customers flying heavily SQ's own C and F products get something serious back, with their PPS program.. and even that one isn't THAT good. LH's HON status is usually easier to make, and offers more benefits. But back to your case..
And for putting C flights into KrisFlyer, that would NOT be a good idea - unless you think 125% milage earning instead of 225% (once you hit FTL, 200% before) is good
So, to make things short:
If you can make FTL (17.8k) this year on M&M, do it. You'll get the Exec. Bonus from January on, making SEN quicker that way. And you'll have lounge access in Europe, and some priority there. Also some advantages on SQ's flights - while it's not *G, FTL definitely isn't "no status" either.
If you can't make FTL this year (The next C flight is January to Europe?) then either make a quick 'n dirty A3 *G for 19k, and once you got it, make FTL, then SEN on LH in 2012 - might be a bit hard to make it to SEN, but with 3 C flights to Europe, and some connections there, and some flights in Y in Asia in 100% Y, should be still possible - and you always get *G benefits, even if you put the miles then in your M&M account.