Ian,
Your question raises the thorny issue of whether the Northern Soul scene (or whatever people want to call it) is about the records or the music.
Of course it makes sense to play the music from the most convenient source but then owning the records becomes a secondary, possibly marginalised, activity. Some people would argue that this would be a good thing because it would stop the ridiculous prices being paid for records because of the lore that only originals can be played at an event.
The thing is though that the lore is still in place and probably the only acceptable way to play from a laptop or similar in today's scene would be to carry a box of records and (as someone else said) hold up the original during each tune. Incidentally a similar thing does go on already with people carrying originals and playing bootlegs to protect the original's quality and thus value.
I actually support your suggestion because I think it would bring more diversity to a scene that is becoming polarised around ridiculously expensive records. The playing of lesser priced records is becoming frowned upon because everyone can have them, cheaper records no longer sell because the record buyers are now concentrating on the higher priced items so they can DJ.
I doubt the scene as a whole would accept that playing the music rather than the original record is more important because it has grown up around the premise of owning the records being played. The fact that formats have moved on is ignored.
As time has gone by owning the rarest and most expensive records is seen to give people kudos, social standing almost. My missus still takes the piss out of me after hearing someone in the 100 club queue in the late 90's say in hushed almost reverential tones "He's got The Cashmeres" whilst pointing to someone further up in the queue. Sounds like an irritable rash if you don't understand.
I've made a similar point before about buying bootlegs, I don't see the point these days as you can get almost any sound you want on CD or mp3 so why buy a bootleg? The answer is so that you can play the vinyl without paying the money for the original, you can have a record collection (of sorts). This made sense when the format of the day was vinyl, it isn't any more but people still buy bootlegs.
I still buy records for my modest collection, mostly cheap but possibly once a month something a bit more pricey. I buy and sell records I don't like or already have to fund this hobby but I'm finding this more and more difficult to do as the cheaper stuff is difficult to sell as I've aleady said. This will stop me buying expensive records because I feel my hobby should be self-funding. Hopefully I'm not the only one because this situation should cause record prices to come down in the future, already some sell-offs are apparent on UK eBay (and on this forum) so I can sit tight and wait untill the rush starts and then carry on my collecting for less outlay.
So, in short, I hope your suggestion is taken up across the land then people will not need the records to DJ, the scene will prosper as younger people will discover the music, record collecting will be for anoraks not look-at-me DJ's and conversely DJing will be done by DJ's.
Errrr ..... England will win the World cup, America will become a pacifist nation, We will have politicians we respect etc etc
Cheers
Paul