I am looking to build a bike for my father in law, who at 85 has had a hip replacement so can no longer get his leg over.
Jokes aside, when did he have the hip replacement? Once the surgeon signs him off for full range of articulation, getting on a normal bike should be possible unless something else is preventing it. I'm sure Mercian would build a Mixte if asked, but you'd get about the same stand-over height from a rigid carbon 29er MTB, which would almost certainly be cheaper for any given weight.
Jokes aside, when did he have the hip replacement? Once the surgeon signs him off for full range of articulation, getting on a normal bike should be possible unless something else is preventing it. I'm sure Mercian would build a Mixte if asked, but you'd get about the same stand-over height from a rigid carbon 29er MTB, which would almost certainly be cheaper for any given weight.