I don't know what your genetics knowledge is but you sound more informed that me about population genetics (I am a cytogeneticist). However, what I do recall about neutral traits, such as blond hair I presume, it is likely that Hardy-Weinberg equilibrium would be maintained in the population. If there is selection against blond hair, then the situation might lead to reduced frequency of the alleles involved. It seems more likely to me that there could be selection for blond hair, although I am sure there is no evidence for that.
In the case of achondroplasia, only a single mutant allele is needed to cause the dominant trait/syndrome. However, in this case, two mutant alleles caused a lethal condition called thanatophoric dwarfism. Therefore, there is selection against the allele, so I don't think we can expect an increase in the frequency of achondroplasia. On the other hand, most cases are caused by a new mutation, so if there are environmental caused for new mutations then we might expect an increase in the frequency of achondroplasia and other dominant syndromes.
The genetic terms recessive and dominant do not mean the same as the they do in ordinary english. Genes do not get eliminated because they are "recessive", they only get eliminated if they are selected against in a specific circumstance. If they are not selected against the gene frequency does not (indeed can not) change. This of course assumes the population is large (if it is very small, it is possible that either gene can be eliminated by chance). The mistake is the assumption that dominance means the gene dominates the recessive gene at the population level.
This is not what the word means. It simply means that the dominant allele is the one that manifests it's phenotypic consequence in an individual that has both dominant and recessive alleles for the gene. Indeed, the whole point of Mendel's demonstration of "segregation" was that the recessive gene could be recovered from a heterozygote in EXACTLY the frequency that is predicted assuming that it had not been dominated (eliminated) by the other allele.
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