And this is different from how people usually play how? The only bonds I ever have are the ones from taxes while on campaign. Also, if someone hoards golds instead of bonds, they get taxed for gold. If this change were implemented, while you may be able to hoard gold for all eternity if you were to get outside the reach of the taxman for gold (which, from what I have seen, has only been suggested for prison), you could only receive bonds as you would more than likely be outside your duchy and thus receiving bonds anyways. Which would be taxed.
I'm not sure what you're saying happens here. Right now, bonds and gold both get taxed equally. If you have 200 gold, and the tax rate is 20% over 100, you'll get taxed 20 gold. If you have 200 bonds, with the same tax rate, you'll get taxed 20 bonds.
As things stand, if you have over 200 gold + bonds under that tax rate, you
will get taxed something. You can't just choose to pay no taxes this week by dumping it all into gold.
Under your proposal, anyone who doesn't feel like paying taxes will be able to dump all their money into gold just before tax day and pay no taxes that week.
So, again:
no.