was it ever considered to include Wesley in the Titan-novels?
I'm sure all the possibilities were considered.
It's not as if all the thousands of now-older TNG Wesley fans (he got the most fanmail during the first four years of TNG on TV) would come flocking to the new Titan
novels if Wes was aboard. Coming back to Starfleet after many years as a Traveler would probably make him very tricky to write, and maybe he'd be in better company over on Excalibur
Similarly, the new Enterprise-E
first officer, Martin Madden - who appears in the NEM script, novelization and the DVDs' bonus scenes - was also ignored by the events of "A Time...", although KRAD did give him a salute in "Q & A".
which came earlier, the concept for ATT or Titan
"A Time..." was originally conceived as a twelve-part novel mini-series (or six duologies) to explain all the changes audiences may have noticed between the canonical adventures INS and NEM. The mini-series (Feb - Oct 2004) was scaled back to a nine-parter. The Titan books (April 2005 - ) were being developed about the same time.