If we peg HBD to 75 cents worth of Hive... that's exactly the same thing as pegging it to $1. Nothing has changed.
That was the rationale for my 'locked long-term value' idea (which I briefly explained here) instead of the flat 25% fee.
The "B" in HBD stands for the fact that 1 HBD can be converted to $1 worth of HIVE, automatically, at any time, with zero third-party involvement. However, that also represents a vector for attack.
I agree with @taskmaster4450 that we need to take any such attack vector seriously. There are at least two ways to deal with that. One way is to exact a high fee for the conversion; however, as has been pointed out, that in effect just makes it a HIVE 3/4-backed Dollar instead of a HIVE Backed Dollar, which just adjusts the peg from $1 to $0.75.
My thought was: What if I can always get $1 back for every HBD, and that I can do that automatically, at any time, without a middleman (so that it remains a truly HIVE Backed Dollar) but that when I invoke that feature, it pushes a portion of my liquidity out into the future?
It shouldn't matter, from an invested-principal standpoint, as long as HBD remains stable. I will still earn interest on my suddenly-illiquid HBD, I just can't spend it until some future time (I initially suggested one year, but maybe 6 months or even 3 months would suffice).
The point there is that if my intent is to wreck the value of HIVE by attacking the automatic-conversion mechanism, I have to forfeit a large fraction of my principal to accomplish that. Make doing so painful enough that it won't be worth attempting (or at least much less so).