The tool that we have seen that ninedee_golf_tdi used to be expensive and not likely to be a loaner tool. It is a bit complicated to use and has breakable parts. I have purchased one and will use it as a loaner. The tool must be 'purchased' and then, when returned, if all the parts are there and not damaged, we will return all of the expense, except a reasonable loaner fee. If you are interested in the tool, please call or email, preferrably.
Sometimes this is not an issue major issue except for the cel light and I would defeat the cel like csstevej suggests. In other words, choose your battles. This one may not be worth the fight.
When removing gp's while the cylinder head is off, we do not EDM. We drill out, which is cheaper and quicker and honestly we have had a 100% success, as long as there are not secondary issues.
Impact wrenches? WHAAAAT?? I guess you must mean a hand impact hammer, but that is a really big MAYBE. I do agree with using penetrating oil, either the 'home brew' Russe11 uses or any of the others...Kroil, PB blaster, etc. We will even build a clay dyke to hold the oil against the plug. For extended days, each time the engine is turned off and cooled down, add some more penetrant.
For actual removal of the gp, without snapping the head... you must understand that the hex head is attached with a thin shell of steel to the rest of the gp. I don't know why they make it so weak, but the official writing by Bosch recommends setting a torque wrench to no more than 33 ft lbs (be sure your torque wrench is accurate...) and do not exceed that torque or the head will snap off. So, the effort is the get the gp to MOVE. Either direction is fine. We have worked a gp for better than 1/2 hr to remove it, which beats drilling out a busted off one.
I know, why would I tighten it when it will not loosen? Don't ask any more except that it often works. We will hammer the area around the gp.. anything to get it to move, but if the gp will not budge at 30 ft lbs, we will consider the alternative, which means we stop and leave it alone. Choose the battle for another day, like when the cylinder head is off.