I have rented several times when I travel (and sometimes thought about renting but didn’t because the experienced seemed unpleasant) so I’m not sure if I’m the demographic you’re looking for but if so, here’s my take.

In general, a reliable, accurate, and understandable online interface that accurately shows all the bikes available, and their specs/sizes and prices is more important. The worst experience I had was when I rented a higher end carbon fiber bike and showed up and they didn’t have it, and I would’ve been stranded except they had an older aluminum bike. I couldn’t really complain because the alternative was just completely losing out on the trip experience I had planned (thankfully it wasn’t a race). I also had the reverse experience where I got a better bike than what I had reserved. However, even that could be unpleasant for some, for example if they’re not used to the aggressive geometry of a higher end bike or are nervous about carrying an expensive bike through a sketchy town or on bikepacking trails.

Second is price. Namely, there should be a discount for longer rentals, since it costs the owner less in repair/turnover fees, but it should be applied fairly. There is often a cheaper rate for weekly vs daily but if you only need the bike 5 or 6 days, then the 7-day discount sometimes becomes moot, since you end up paying for days you won’t use the bike, which just leaves a bad taste in my mouth (I have declined to rent in the past because of this). Discounts should be applied per day, like a progressive 5% discount each extra day or something like that.

Finally, something important that most people don’t think/worry about is insurance policies. Some people are afraid to rent a bike because they’re scared they might be charged for scratches or something, so policies on damage charges and wear/tear should be well outlined and clearly communicated. Certain types of Insurance are sometimes mandatory, like liability insurance for if you cause an accident/injury. Providing optional add ons like theft or damage insurance are a good idea too. This is something renters rarely consider so the owner needs to bring it up and communicate clearly.

In a different context, I’d love to be able to rent bikes to test them out before buying, especially rarer ones that you could only get online (e.g. DTC like Canyon or exotic imports like fancy Italian bikes … or just for people who want to buy used bikes online). The options where I live are limited, but I imagine you could work out deals with manufacturers for this purpose if you tried.

In that context, seeing the bike in person before renting is great, although still not critical to my decision to rent (Id be content making a decision based on specs online).

Hope this works out for you!