Not silly at all.

I was having the same thoughts as I was posting the above descriptions of the 'problem' (pitfall, literally). In theory, such an auxiliary piece could even be held in place by a flush mounted screw and thus be removable (though the parts would be quite small). If one had a 'spare' magazine (such as a surplus 'Greek Contract" mag for a M1903) that was expendable, one could braze or weld material onto the front guide area and machine it to size / shape. Perhaps it would be easier, however, to fabricate and add a 'ring' just as the Steyr engineers did with the M1924 onward. All of this is speculation as I have never modified an MS magazine nor do I know of anyone who has.

This is the Magazine 'body', or housing, from a 6.5X54 'Greek Contract' MS (and is currently available on Ebay) It is the same as that of a M1903:

It is my understanding that the 'ring' added to magazines from M1924 onward 'fixed' the issue. My only MS is a M1910, so you'll have to ask others for accounts regarding actual use of different projectiles on M1924 (and later) Mannlicher Schönauers.

Another idea, if one was really fond of a particular spitzer load for their MS and wanted to do a proper job of it, would be to craft a precise model of a new lower housing and spindle of wax to fit the spitzer (or of another material, build a rubber mold around it and shoot some waxes), then make metal copies using the 'lost wax' (investment) process. CAD and 3D printing could be employed to make the model, then hand finish. Wax casting being a repeatable process, once one was made they could be reproduced indefinitely.

For me, I'll just continue building my M1910 rounds as close to the original DWM 531 profile as possible and / or try Kuduae's formulae. I have a good supply of 270 grain RNSP for can, bottle, and gong killing and am still searching for the ideal 'unleaded' hunting projectile for the M1910.

These look promising:
Peregrine Solid