To start and finish with,
- Optional machines to work with
is not an English sentence.
It is an English Noun Phrase, with an undetermined head noun machines, modified by an ambiguous modal adjective optional -- optionality of the work or the machines? -- and a subjectless relative infinitive clause to work with.
There are a lot of ambiguities and missing referents in this noun phrase that must be resolved by the (hopefully well-trained) reader. With that many problems already, I don't think the risk of additional outrage over a stranded preposition is even worth considering.
Executive Summary: Start over.