sheepdog,
It is your money and certainly your choice as to how to spend it but IMO you may as well drive down the road throwing money out the window.
A little background - I am Master class in Hunter rifle and AAA in Standard rifle, I use my Hunter rifle for both classes. I have won quite a few State matches, Regional matches, and have been fortunate enough to win some Nationals matches. I also have Grand Slam pins from both Hunter rifle and Standard rifle in Smallbore and High-Power. I have not shot a 40 yet but I do have quite a few 37/40 and a couple of 39/40 under my belt. I am not posting this to brag but to let you know that I have some experience behind my suggestions and have a pretty good idea of what does and doesn't works.
I am also a few years older than you, so I know what you mean about the aches and pains associated with shooting off-hand at an advanced age.
I have no idea what level you are shooting at, whether it is Club level unregistered matches or Registered matches, or if you are using regulation sized smallbore rifle silhouette targets. At the higher level of smallbore silhouette competition if you check the rifle racks, or watch the shooters you will notice that well over 75% of them use two items - an Anschutz 1710 0r 1712 and a Leupold 6.5-20 scope with elevation and windage knobs. Most shooters who finish at, or near, the top will be using mid-level match-grade ammo with a 40 gr bullet, with a muzzle velocity of somewhere around 1050-1100 fps so it does not have to deal with the transonic issue. Most of all of those folks have been down the road of searching to "buy" points with a "better idea", if what you are proposing worked believe me folks would be doing it.
As far as adjusting scopes that is a non-issue, I do not know of anyone who is a serious competitor who tries to hold under and over for his sight settings. And if you are not adjusting for windage then you are giving up a lot of points (perhaps this is what's behind some of your "flyers). Scope adjusting in a smallbore rifle silhouette match is a necessity to be competitive. It is as simple as putting a piece of tape on the stock or scope with your "come-ups", for example mine is marked C-0, P-1.3, T-4.1, R- 7.3. It requires nothing more than looking at the scope to be sure it has the proper setting before starting to shoot the bank of animals.
To keep a scope from tracking issues all that is required is an occasional "excercising" of the knobs. This is nothing more than once every month or two run the knobs from stop to stop, this spreads the grease around and keeps the scope from sticking on an unlubed thread which develops from constantly adjusting the scope through the same limited movement.
You mentioned that your rifle shoots the same size groups off the bench as it does off-hand, if you can shoot the same size groups off-hand as you can off the bench then you are a "hard-holder". As a matter of fact I do not know of anyone else who can do that and I have shot with some of the best in the sport for a lot of years. What size groups are we talking about at 44 meters, 60 meters, 77 meters, and 100 meters?
My rifle, off the bench, shoots around 3/8" at 44 M., 1/2" at 60 M., 1/2"- 3/4" at 77 M., and one inch at 100 meters under ideal conditions and my off-hand groups are at least twice as large under ideal conditions.
May I suggest that before spending money on your idea visit steelchickens.com, go to the rimfire silhouette forum and float your idea there for some additional feedback. Good luck whichever way you decide to go.
drover