Northland,
I don't think anyone has ever lost money on
BX23s even if they end up trading up eventually. Those things hold their value very well so I would not fret. Your tasks seem split between around the house/driveway duties and the woods. Your BX will excel at the house/driveway stuff. Obviously a bigger machine would be better for the woods but if you are careful and take your time you can certainly accomplish most everything you are trying with the
BX23. Just watch that ground clearance.
I am a grapple fan for working in brush and woods so you might consider adding a grapple to your bucket to help out there. I think that would be more useful than a backhoe thumb. You are likely to use your FEL more than the BH (almost everyone does) so I'd advise accessorizing the FEL before you worry about the BH.
By the way, with a subframe, the regular CUTs are just as solid for BH work as the
BX23/24 so don't worry about that if you eventually upgrade. I don't think the work you are describing is a good match for a
B21 (as Henro was hinting) as that is really a construction optomized machine (and a fine one).
The B series (and the long anticipated update to it)
would be my choice in the Kubota line as an upgrade to the BX. Mahindra, Kioti and TYM are all excellent tractors that compete directly with Kubota and should be considered too even though they obviously don't have the Kubota market share or dealer network. Each of those machines can be turned into a nice TLB.
Good luck with your new BX.23. I am sure you'll have a lot of fun.