It's okay, you're not coming across as awkward - rather than downsides, I see these as understandable concerns. It's a matter of scaling up - and, as you say, "responsible people" should not feel cut out of the loop per se. The machines I've seen crush the cans and plastic bottles anyway and that reduces space taken. The rest is logistics. As for the machines being overwhelmed, I can see that too - so the scheme again needs to appreciate the scale. Power concerns - I don't know the specifics but I am led to understand that they are energy-efficient and there's an opportunity to feed them from renewable sources - like anything else can be.
Not downsides but challenges - if the will is there and the organisation is effective, you, the "responsible person" should not feel overlooked or side-stepped or anything like that.
This scheme has the great potential to be part of a joined-up process aimed at reducing waste and specifically the perniciousness of plastic pollution.
As a software developer working on our companies systems, whenever I make a change, I always look at what the knock on affects are and try to not introduce bugs into the system where none exist, so that's where my train of thought comes from.
In Aberdeen city centre the street bins for rubbish have solar panels which power the crusher so they fit more rubbish in and don't need to be emptied so often (reduces fuel used by bin lorries). Could do the same with these.
According to the BBC, of the 13 billion of these items sold, 3.5 billion do not get recycled, so anything that helps to reduce that has to be welcomed with open arms. However, there are currently 8.5 billion that ARE recycled, so that is adding a total cost of £1.7 billion to these people. Now what does need to be taken into consideration is that, if these people now move from the current method of recycling to the deposit refund scheme, this is going to require the manufacture of millions of bins and solar panels (for example), so there is a big start up cost, both in purchase but also the obtaining and transporting of the raw materials and the production and shipping/installation etc.
Therefore, the scheme needs to try, as much as possible, to retain the current recycling for the 8.5 billion bottles and then be used mainly for the recycling of the extra 3.5 billion.
I'd also like to see a system brought in, where you log each bar code to a purchaser and then, if that bar code turns up from roadside cleanups, the originator fined for littering.