How are you going to prevent people burning your domain names?
Any expensive domains I buy, I'm careful with them - I build links slowly to start with, don't do anything too spammy, no hidden links and so on. This is all due to the fear of losing an expensive asset.
If I'm renting, I could cut corners and do high risk things, since I don't really have anything invested in it. If anything renters might be more likely to take this approach from another point of view too, since they need to rank it quickly to make money and stem the cashflow loss coming from the monthly payments going out.
I think I'd rather sell domains or develop them - trying to rent them out seems a poor proposition from the owners point of view to me.
Also it might be worth adding in a better way to search them. You have too many low quality domains in there, and you're asking per month for them an amount that I honestly don't think anyone here would pay you once, to own the domain outright. All the poor ones are making the decent ones hard to find. You've already ranked them 1-5 stars, could they not be searched/sorted by those too? At a quick glance your portfolio looks low end, which is a shame when you have killer domains like finance.co.uk and wine.co.uk in there...