OK, the following are the 1.5 core promotions:
ARB_vertex_buffer_object
ARB_occlusion_query
EXT_shadow_funcs
and a few tokens were renamed. LWJGL already has these as extensions, including the GLSL ones (which are not in the 1.5 core) and the renamed tokens as well. What you are saying is (correct me if I'm wrong) to create a GL15 class (like the 11-14 ones), that contains the above extensions. And remove the separate ones. It's no big deal actually (no delay worries). Just a few cuts&pastes. Is that it? Tell me and consider it done.
Just a personal note... I'm not sure I like this merging. Especially for such important extensions. I mean, it kind of ruins the clean-up we're doing with all the extension splitting. And unless we keep them separate as well, the fact that VBO (for example) will be inside GL15 is confusing, since it's supported in much older cards too (with not even 1.4 support). Any thoughts?