I install no-design-time packages simply to let IDE know where to look for it's units.
You don't have to. I simply compile the package, I think it's even enough to just open the lpk file in the package editor. Then the unit path is known to the IDE and you can add the runtime package to the requirements of your project. FPSpreadsheet works exactly this way.
Working with runtime packages helps to keep the IDE slimmer. And it avoids the naming conflicts. But of course, I think too that a "u" prefix is not specific to identifiy the LMath units. I'd prefer an "lm" prefix for all LMath files (I hate dotted unit names...), the package should be renamed with a Pkg suffix, like lmGenMathPkg.lpk. And since these are breaking changes you should also take the opportunity to replace these ugly names: ULineAlgebra --> ULinearAlgebra or ULinAlgebra, UPolinoms --> UPolynomials. Moreover I see that the LMath directories are labeled with inconsistent casing: in some of them, the "u" is uppercase, in others it is lowercase -- this is a pain in case-sensitive OSs. CamelCase is fine with me, but please be consistent.
I could not find lmath_all.lpk in trunk.
Sorry, my fault - I had created this package by myself some time ago when I did my first tests with lmath.