I don't see there is a problem landing or departing SE at LCY - any more than at quite a lot of other airports where an engine failure during the approach would definitely land you into houses. In fact LCY is better because one has the river.
If LCY management say "no SE" during specified periods, or that every pilot landing there must wear pink underpants, that is within their rights. They don't have to give or invent a reason - same as LHR bans GA without giving a reason. Or they are entitled to give a totally bogus reason.
I can see the CAA not liking an overflight of LCY (and there is any number of pilot forum claims of prosecutions under the glide clear rule - not that I have ever seen any of these substantiated) but if one is landing at or departing from LCY then glide clear doesn't apply.
I don't see any need for a risk assessment. In any case, it is self evident that GA can safely operate at LCY so any risk assessment would be bogus.