1/ it's been done a lot in the past all around the world and I can't think of one single accident directly attributable to "coasting in".
( it's not something I see a need to do however let's keep it in perspective shall we )
2/ how many backups do you need? You might as well fly an Aircraft with 10 Engines, 5 Hyd systems, 2 accumulators and an Anchor if you are that "conservative"
Er, nit old chap, I bow to your obvious statistical knowledge of operations all around the world involving engine-less taxying, but you seem to be implying that having your engines running as you manoeuvre onto stand is too much of a 'back-up' ??
I'd love to see you try this on something like an A330 - keeping on the centre line with only a few meters of clearance each side, and stopping within half a meter when the stand guidance says "STOP" !!