I think it is inevitable that it would come at the cost of poorer domestic results, as we'd be fighting on an extra front.
'Smaller' teams who sneak into Europe tend to fare poorer the following season. Part of that might be because they exceeded expectations the previous season and are simply regressing to the mean, but it's common sense to see that when Burnley got into Europe, they finished with 14 fewer points the following season.
There are exceptions, it doesn't always happen, but if we didn't invest in the squad to manage those extra games, we could struggle.