And along came an idea....
You may have heard about the CobbWeb aerial. Essentially, this is a cluster of dipoles for the bands 20m, 17m 15m, 12m and 10m. The cluster is fed via a coax choke.
Maybe there is a way to squeeze more out of this aerial. The amount of wire in the dipole array creates a decent capacity, I figure.
It may be worth a try to build such an aerial, feed it with RG-6. And, for MF purposes, use the feedline's shield (and core) as vertical and the dipole array as capacitive load. The rf choke could further help to increase the load on the (very) short Marconi for 600m.
This would be somewhat like the antenna disclosed in the U.S. Patent 3,569,970, (see Figs.7a,7b) but using the CobWebb in place of the stretched dipoles.