Chapter Text
The Flavour Text of the Clawed Bomber's 'Dimensional Bomb' attack is quote "Blown into a rift in space-time!" and the affected party member disappears until the end of the battle.
And I do mean completely disappears, they can't be retrieved, you can't see their status and they don't even show up on the Results screen at the end of battle. Once the party is out of combat the affected party member is returns, on 1 HP, MP unaffected, which is standard for a character who was KO'd and not revived before the end of combat.
What if characters normally return at the end of combat because some sort of Party power draws them back? Combine that with, what if the whole Party was hit by the 'space-time rift'? Which means that there is no Party member remaining to anchor the Party back to their own dimension.
Well that could be how a Blue Dragon crossover begins.
Without a Party member to anchor them they find themselves drifting deep into the 'space-time rift' and eventually they are spat out in a completely different dimension. The dimension of whatever universe you want to crossover with Blue Dragon.
Depending on how you wanted it to work you could set it either before Nene's defeat or after.
Before Nene's defeat means you would need to bring the whole Party along (Shu, Jiro, Kluke, Marumaro, Zola) but would give an urgency and high tension to their attempts to find a way back home. (The Mecha Base, accessible by Mechat, in the ocean near the Forest of the Dead, has Clawed Bombers.)
After Nene's defeat means you could wildly vary which group of Blue Dragon characters you want to bring along and how perturbed they are by their sudden dimensional displacement.
Given that it is 'a rift in space-time' some degree of time travel is also possible.
All in all I'd say ambushed by Clawed Bombers and blown up to find yourself in a different universe is a pretty cool start to a crossover.