This is horribly complicated and potentially dangerous too.
Yes it is, I think we should just have a UK (or Europe) wide TA of say 10,000' - just to pick a nice round easy number. That would leave most light aircraft operations where we wouldn't have to bother with it, or the completely pointless system of quadrantal FL's. The base levels/altitudes of some CAS would have to be redefined, but how hard's that.
It's rubbish that being at the appropriate quadrantal gives any kind of protection from a collision with other aircraft in class G airspace. What it does do, is make being terrain safe and staying out of airframe icing conditions unnecessarily tricky other than in summer.
For example;
MSA of 4,600'
Freezing level of 6,000'
TRK(M) of 300*
to keep it simple, let's say the QNH is 1013mb, assuming we are IFR in cloud, we are obliged to be at an even+500 FL, FL45 is below MSA so can't be used, FL65 will put us in known icing, so that's no good either. If we didn't have to use a low TA and FL's, we could simply pick any convenient altitude between 4,600' and 6,000'