Hi Jackdaw and welcome. There are a few people here with experience in this sort of thing who no doubt will help you.
For everything it sounds like you're trying to do (with the possible exception of HF bands above, say, 20M) my architecture of choice is a class D or E RF deck with a PWM series modulator. I won't go too deep into the reasons on this thread but I've always considered it a no-brainer.
Due largely to improvements in FET technology, reasonably powered, highly efficient and compact HF rigs are now easy and actually the newer FETs will work on higher bands. This sort of rig is also easily replicable and scalable.
There's loads of info out there on this technology so apologies if you've already found these and others like them but here are a couple of sites with information on the theory and some designs you can look at and have a play around with:
Look for FAT5 and PUWMA, although there are also some more conventional series modulators on the sites.
There's also a good writeup here of a rig for MW:
http://www.maxmcarter.com/classexmtr/ci ... iption.php
There are quite a few hams who are refining the above designs and techniques. Much of their output is on the forums at hfunderground:
You might find the work that's going on around SiC and Gan FETs interesting, and there are some nice variations on the "FAT5" type arrangement which will make your RF deck quite a lot tidier. You might have to reverse engineer some of it from the pictures though, as it's quite experimental by nature.
I don't know what your electronics chops are like or how confident you are with building this kind of stuff but there are people (on hfu in particular) selling gear and there is one guy here in the UK who posts regularly on hfunderground and I believe has some shortwave GaN stuff under development.