I don't really know if they will close the loophole or if they'd even be able to. One problem is what happens with all the bikes that are already on the road, will an A1 licence holder still be able to ride them? Will another A1 holder be able to ride the same bike if they buy it used? Will it depend on when the rider got their licence (before or after the change to the legislation)?
The second problem is there's a reason why electric bikes are rated on continuous power and not peak, they can't hold peak power for an extended period like a gas bike can. The real issue is the way in which continuous output is defined, assuming my understanding of it is correct. Instead it should be based on the absolute maximum that the motor can sustain for a certain period of time before it overheats and has to reduce power. However this is a hard thing to test and would require a bit of trial and error, plus it would depend on environmental factors.
To the first issue, this has happened in the past several times and once registered, the bike is only bound by the legislation at the time of registration. Otherwise my ICE bike wouldn't pass the emissions test.
To your second point: Not all bikes can do it, but Energicas can due to oil cooling

Your proposed definition is the actual definition of continuous power: 2.4 of
https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:42006X1124(03)