There is a range of different interpretations of the ICAO standards on this topic. To give two examples, in the US a clearance to land may be issued while there is one or more aircraft sill in the air on the approach ahead of the aircraft that gets the clearance - this meets the rules if, as you point out, there is a reasonable assurance that the runway will be clear when the aircraft gets there. On the other hand, in the UK, where I did most of my controlling, the rules are that landing clearance cannot get issued until the previous lander has vacated or the previous departure is airborne (I think it used to say not before a departing aircraft has crossed the upwind end of the runway).
Personally, I prefer the UK way but that may well be because that was what I was brought up with. But it does mean that landing clearance sometimes isn't issued until the wheels of the lander are floating over the runway (although the UK book does say that the aircraft should not be allowed to cross the beginning of the runway until the clearance can be issued - I think this is one of the most commonly flouted rules) whereas, in the US, a clearance to land could have been issued some miles earlier. There are strengths and weaknesses in both systems.
Certainly from my experience, when things were going to be 'tight', as the controller I made sure that everyone involved knew what was happening and knew what to do if the plan didn't work - as waxo says, everyone must be on the same page.
To answer the original question, there is no absolute minimum distance by which a landing clearance must be issued although individual aircraft operators' SOPs or ATC unit procedures may specify something. For example, during LVOs there is almost always a minimum distance by which the clearance is issued because the need to protect the ILS signal by a specific range means that the runway will then be available.
There are many, many variables that affect when a clearance can be issued and to try to write procedures to cover every situation is probably not going to work and would undoubtedly result in less flexibility, and more go-arounds or lower capacity. What might be better in my view would be to ensure that the controllers know their jobs and are able to apply professional judgement to any situation.....but I am now getting very old and I recognise such ideas do not fit with modern ATC.
Overall, although there are many discussions on the topic, often starting when someone is exposed to a different way of operating to that with which they are used, it's something that appears to be quite quickly understood and, ultimately, which works in most situations regardless of the rules being applied.
Finally, I would advise caution about making assumptions about why the rules are written as they are - the 2 mile range mentioned for radar approaches was, I think, put there for other reasons than you surmise.