I only noticed different loadouts from old versions of new jet era mods, like Phantom, Crusader and such. Haven't run across dreal breakers in WAW yet.
If you stick to stock DGEN campaigns in WAW you should be good for starters.
Stabilising the Jet Age, loadouts, FMs, hooks and Engine MOD has been a loooooooong road. While CUP did a lot to help develop the Jet Age it is in B.A.T. that we are beginning to reach a stable point. By B.A.T. Expansion Nine we will be presenting stability and the latest, all fixed, code for many areas.
As mods developed code, objects and even component names were changed (beyond our control). Missions made in earlier environments would inevitabley go obselete. One of our core goals with B.A.T. is to stabilise the mission environment. Anything being made fresh in B.A.T. now, or converted using the B.A.T. tools and setups, will remain forward compatible as long as we have B.A.T.
That's why my campaigns are being released again, 56 of them this week.
There was some good stuff in the past, although don't ever forget that earlier campaigns, however good they seemed at the time, lack so many of the resources we have now. To a practiced eye most look a bit bare these days. The well written ones are worth an upgrade but nobody wants to go backwards.
Regarding DGen, there is a modded DGen system out there and its perfectly feasible to test it in B.A.T. Default DGen is un-touched.
However, when you know your way around the new FMB, when you have started to skin statics, place sound effects, work out parking and taxi-pathways, define formations and patrol waypoints and introduce variable weather, AI skill, Ground Control Intercept, Artillery assignments. When you add this to the largest flightline in Il2 history, with more vehicles and tanks and ships too. Anything else is, frankly, poor fare by comparison.
Some mods were changed and some didn't work as smoothly when added to the later versions of Il2. When people question
"why was this mod left out or missed? - Please bear in mind that I added and tested every single mod, well over 1000 new aircraft tested, more than 400 new maps and countless vehicles, objects, ships and tanks, to a vanilla 4:12:2m, personally, one by one, over a period of 4 years, to get to where we are now.
It was not a smooth progession either. The new code broke some things and changed others. It was a very bumpy road at times. Thousands upon thousands of details, over several years, to get to where we are now. Despite all this I still listen to further requests, and still try to rescue and reinstate many old mods alongside the new ones.
The great thing is that in the process of this building our small core team has received so much assistance. We attracted some criticism, at first, but we have also made many friends. So many great modders have joined us and recognise the legacy we are attempting to build and keep. The B.A.T. network of expertise and go-to guys is really impressive these days. This thing has grown way beyond what any of us could have imagined!

B.A.T. is, above all else, a mission makers toolkit. We have spent a long time building the toolkit in order to make better missions, to fly and tell stories. The new material that is coming will be head and shoulders above just about anything we have seen so far. Some B.A.T. Campaigns will be illustrating flights that are not possible with any other setup.
Anything old that no longer cuts it, but was well written and interesting, is worth opening up in FMB and sorting out. Me and many others are making those new missions for B.A.T. and rescuing , and upgrading, plenty of old ones too.