Feature modeling has emerged as the de-facto standard to compactly capture the variability of a software product line. Multiple feature modeling languages have been proposed that evolved over the last decades to manage industrial-size product lines. However, less expressive languages, solely permitting require and exclude constraints, are permanently and carelessly used in product-line research. We address the problem whether those less expressive languages are suicient for industrial product lines. We developed an algorithm to eliminate complex cross-tree constraints in a feature model, enabling the combination of tools and algorithms working with diferent feature model dialects in a plug-and-play manner. However, the scope of our algorithm is limited. Our evaluation on large feature models, including the Linux kernel, gives evidence that require and exclude constraints are not suicient to express real-world feature models. Hence, we promote that research on feature models needs to consider arbitrary propositional formulas as cross-tree constraints prospectively.