The problem here is that Omega have had many different ranges of watches that look superficially like 'Seamaster 300' some dating back to the 1950s. You may get more of a response if you were to ask for help with 'Omega SMP' or 'Omega Bond/2254' as people will recognise that and may be more inclined to click in.
To answer some of your questions, the 2500 models were rolled out in about 2008. They simplified the range when they did this and removed the very popular sword hands 2254 and 2255 designs and AFAIK there are no titanium models with the 2500 movement either. Thus, you wont find a sword hands model with the 2500 movement. They did introduce a black dial version of the blue Bond design though.
That aside It wasn't necessarily all good news post 2008 since the case depth was increased slightly, up from the ~11mm of the 1120 models to the ~12mm of the 2500s. Early 2500s weren't always totally reliable either, you are right to hope for a 2500D but they weren't around until about 2012 or so at the earliest. There are indeed several limited editions, including solid gold bezel versions and others but nowhere near as many as with the Speedmaster thankfully.
As you may be able to guess from my tone, I am more a fan of the earlier 1993-2008 1120 varieties, I have owned I think about 9 of them. Here are a few, most now moved on: