If you really like the tone and spl/power handling capability of the Orange OBC410, but find it too heavy why not replicate it: dimensions, internal volume, stuffing, porting (if any), drivers and wiring, but using modern, low weight construction techniques and materials. You should be able to cut the weight by about 40%. Search here for some DIY builds in this forum. There are plenty of pictures and accompanying discussion. Show the pics to your father. He will quickly pick up on what this is all about.
The 3 mm Xmax is not overly generous, but many cabs have been build with those (or similar) drivers, and a lot of good music has been played through them. If the OBC410 has been working well for you then these drivers (Beta 10A) will do just fine in the new cabinet.
If you want to build a new, better cab, choose from the DIY projects you found here. For sure, it is easier to build a louder cab, but it is usually much more challenging to build one with the tone you prefer.