I’ll share a couple thoughts on this,
When I’d started designing the VacExtender, I’ve actually went with this route - basically a condom (like closed end sealing sleeve) with a hook attachment (stronger silicone). While the idea sounded great, in reality, it didn’t work out. The main problem was that it stretched the head but not the shaft (as much we needed for our purpose). As pressure was applied (or pulled), the head of the penis was stretched as silicone contracted and stretched. This was the main reason for the plastic cylinder, to avoid the head stretching (and it wasn’t good head stretching either as when silicone was getting thinner (from pulled force), so did the head. The final result was thinned and stretched head, without the benefit of any feeling toward the shaft. I’m still playing with this version, but it not going too good. I could re-inforced area around the head (so that it doesn’t get thinner and only stretch the head) but production proved to be too difficult (mixing chemical during cure time don’t work well).
As for latex - some people are allergic to some types of latex (depending on chemical makeup), but majority of people do not. However, latex is not a good candidate as durometer/elasticity is not as great compared to a silicone (which also don’t have the allegic property). Simply, its too hard or too brittle to stretch.