Well, I think's there a low chance that something serious will happen. There is some chance that the Guard won't turn up.
(Actually, a good system, considering that this stop was at a checkpoint, would be for all the prosecutions to occur in the same court, on the same day.. so it'd be easy for the Guard to turn up.. also the Court Clerk could list the cases together to minimise the Guards lost time)
If the Guard turns up then you'll have to plead.. most likely guilty... you could plead not guilty but unless you have a loophole or a technicality of some sort I don't how what you'd say. The judge will most likely be well used to everyone saying 'it was the first time ever', or 'I was only going 100 yds' or 'I didn't know' etc.. so the penalty depends on the judge.
You should find out the maximum penalty on StatuteBook.ie by entering in the act and section number from the summons.. probably just a fine but maybe jail time, I'd be amazed if they imposed jail time, that is basically inconcievable.. so a fine, maybe penalty points.
People are criticising the Guard.. maybe he's aware that a covered number plate is a serious offence, the car is untraceable.. what if there's a hit and run, cheating on tolls, speeding cameras etc?,... whereas the licence issue is less serious, and our system is pretty badly implemented, (we should have smaller licences).. so the Guard did display good thinking on the day in my opinion. I presume he did ask for you to produce the licence within 10 days?
I think there should be a zero tolerance policy to 'minor' motoring offences.. no tax, bald tires, dirty plates (and novelty plates with the wrong font or colour), not the licence maybe, but also cracked windscreeens, broken lights and mirrors, illegal turns and use of bus lanes etc etc.. that's the only way people will finally learn.
How are the Guards to know if it a first time offence or a serial offender?.. the only thing is to prosecute everyone and soon only serial offenders will be breaking the law as others will have copped on.
These 'minor' offences should be prosecuted using affadavits from the Guard by civil prosecutors, using photo evidence where possible as it is very compelling and hard to deny, in a special streamlined dedicated motoring court.. (maybe by using a special judge or judges who travel around to various district courts for the one / two days a month when motoring offences are prosecuted)