Is it worth combining upgraded outward leg and normal return (for baggage)?

[iaink]

I’ve got one upgrade voucher that I intend to use to upgrade our (2) outward flights to Business, and come back Economy. The only way I can see to do this online is to book the 2 legs separately (as it only seems to support using the voucher for both legs). My question is (and I couldn’t find the answer elsewhere): Is there any disadvantage to this (and therefore should I do it over the phone)? I have a feeling that I’ve had the higher status baggage allowance applied to the full itinerary when I’ve done something like this before, which would certainly make it worthwhile (i.e. hold luggage included for return leg).

Thanks

[iaink]

Actually I think I’ve answered my own question, as I just spotted that the Avios-booked return leg includes a checked bag, even in Economy. So does anyone know of other reasons to keep both legs on one booking (other than convenience)?