IMHO a bad idea. If you want to do this properly with 2 crew, then the co-pilot should be equally qualified (i.e instrument -rated) and experienced in 2 crew IFR operations. The only compromise is that he/she could be experienced less in terms of hours than the Captain.
I know how you get instrument rated, but following your argument, how do you suggest a low timer should get experienced in multi-crew IFR operations?
Or is it safe enough to have the 250 hour guy (or the inexperienced recent VFR guy) assist in carrying 12 roughnecks, but not safe enough for the CEO - and all that with much less workload in a fancy SPIFR EC155 rather than a dual pilot S-76A or AS332L1?
Back on topic: the EC155 probably cost £1 or £2 mio more than a comparable alternative (I stand corrected) - just think about it: for £1 million you spend in excess because it may look better, you could hire 3 pilots (let's say 2 captains, 1 FO) for 5 years and still pay 'em a somewhat decent salary!?