I have weighed in on this concept before, but I will do so now with a bit more detail.
I would say a decision needs to be made whether the initial long-term HBD instrument should be treated as a 'bond' or as a 'certificate of deposit'. A 'bond' would pay all the interest plus return the principal at the END of the lock period; a 'CD' format would enable withdrawal of the principal at any time, but with a penalty (typically all or a portion of the accrued interest).
Personally, I think the 'CD' format would be better, as it is much more flexible for the depositor and doesn't require secondary markets if the depositor has a change of heart and needs immediate access to the principal.
Shortly after my wife and I got married (25+ years ago), we had some cash we wanted to get a yield on, but we wanted to have access to it if need be. In other words, we had no immediate needs, but we were expecting our first child, we were renting but considering purchasing a home, etc. So flexibility was important to us.
I ended up getting multiple CDs with various durations (e.g. 3 mo, 6 mo, 12 mo) at various interest rates, and I spread out their initiation dates over the first few months. And, when the shorter-period CDs expired, I could roll them into their own longer-period CDs, so that I always had at least one CD renewing within 30 days. This is a process known as a 'CD Ladder' (sometimes done over years; I did it over months, to maximize our liquidity).
The net result was, if we needed access to cash, we could either [1] wait a few weeks until the next-to-renew CD was redeemable without penalty or [2] redeem whichever CD had enough cash in it to meet our immediate needs and had the least penalty.
The nice thing about that setup was, although it took a little bit of up-front calculations and legwork, once I set it all in motion, I had the benefits of longer-term yields with immediate access to 1/12 of my money at any time, penalty free, 1/6 for a modest penalty, etc.
My suggestion would be to follow the CD model and make it so that the 'CD Ladder' strategy is built in (i.e. don't force savvy investors to jump through a bunch of hoops to accomplish this -- make it easy for them).
@taskmaster4450, I would be happy to draft a procedure and parameters to implement an automated 'CD Ladder' strategy if you think that might be worth further exploration.