New Garmin COM/NAV

What is the meaning of the German "IFR certificate"?

That's the certification of the radio devices. You get an "inspection report avionics" which you have to carry on board and this lists all devices emitting radio and contains a section that says that the aircraft is equipped for VFR / CVFR / IFR. For IFR, it has to be done every year, for VFR every 2 years. It's one of the most useless expenses in aviation.

my shop mentioned something about the new regulations will be implemented step by step so you actually don't need two 8.33 radios until 2017.

2014 for IFR, 2018 for VFR. Again, it's in the law (European this time).

If the outfit doesn't think two 8.33s are needed and will provide the IFR certificate- that's good enough for me, I wouldn't question further :)

I doubt they actually will do that. The radio inspection is usually done by specialized freelancers and the correct information about the 8.33kHz rule will eventually spread.

Has Germany ever actually fined anybody anything for such tenuous avionics "shortcomings", let alone €50k? Practically speaking, for the alleged criminal offence to be detected in the first place -

First of all, it's not a criminal offense but an administrative offense. The law says fine "up to 50k€" and it's within the administration's discretion what the actual fine is going to be, taking into account how severe your infraction is, what your background is (repeated offender, intentional infraction, no regrets, etc.). In the "oh, I didn't know, sorry, will never do this again" case without any actual harm, the fine is usually € 500 which is considered to be the minimum fine for aviation administrative offenses.

and then they have to arrest you and throw you in jail, and/or confiscate the aircraft, because nobody with a brain is going to hang around at that point, and no non-German with a brain will ever revisit Germany if there is a €50k fine waiting.

Oh, the administration doesn't care about such things, they act based on the law. If they get to know about an infraction, they are legally required to take action. Such fines can be collected throughout the EU so you don't have to visit the country. They will not arrest you, administrative fines are processed through mail. If you refuse to pay, they may eventually arrest you and that might even happen in the UK thanks to the EU.

Suppose you fly IFR to EDNY for the Aero show with one VHF and no DME and I really hate your guts. I will take a picture of your cockpit and write a letter to the CAA. They will hate it but they are legally required to take action.

(Maybe a Honeywell rep will do exactly that during the Aero show, given how badly you are talking about their fantastic KFC225 servos? )

The law is the law whether you consider it to be sensible or stupid.

So how come the UK cannot collect speeding camera fines from foreign drivers?

The UK have implemented the Council Framework Decision 2005/214/JHA which makes all sorts of fines enforceable cross border. It was due for implementation in 2007 but several member states have taken longer. Germany took until 2010 and the UK implemented it some years ago. So yes, speeding fines in the UK are enforceable in other EU member states.

The very same law is to be applied for aviation related fines. You cannot avoid a fine in Germany by no longer flying there.

Of course it's not very smart to have all those peculiar national regulations that a freely roaming EU citizen has to be aware of. The only sensible solution is to replace national law by EU law that directly applies in each member state without having to be implemented (and thus modified). That's why in principle EASA are taking the right approach.