It is sad to see it in seemingly un-checked decline, but I'd like to add a bit of hope to the discussion!
I'm going to start by cutting buses and land-trains from there equation. They'd do the job okay, but they'd really ruin the immersion, which if Merlin/Towers truly care about, they should take seriously. I'll also rule out moving the entrance, as FB is a terrible place to have a park entrance, and you wouldn't get the view of the namesake gothic mansion, lake & lawns that make the park so iconic.
(For the record I'm coming at this from someone who's done a fair bit of work in the transport sector recently, so whilst it's different from the theme park industry, there is overlap which may be of use!)
So, what can you do?
- Keep the alignment. That's to say the route or "right of way" itself from the car park to the park entrance.
- Remove the monorail tracks & supporting beams. This is to make way for the optimal replacement, which won't be a monorail system.
- Use the former alignment to install an Innova Automated People Mover (Alstom). This would be a point-point single-track system with a central passing loop.
Why? Well, monorails aren't typically manufactured to be narrow-profile vehicles like the old days (Von Roll etc), they tend to have much larger tracks & larger loading-gauges (width+height of the vehicle) This would mean if you were to replace it with a modern monorail system the entire route would need re-profiling, requiring demolitions of some of our favourite attractions and shops. So not going to happen!
But, an automated people mover? That actually would work a treat. You'd effectively replace the twin-track monorail route with a single-track people mover track (which is almost as wide as the current 2 track set-up, but fits neatly into the alignment)
The alignment very conveniently already has a roughly 130m stretch slap bang in the middle where it could be widened to create a passing loop, thereby allowing 2 trains to operate simultaneously. This is between Sub-terra & The Haunted House. You'd remove the existing loops at either end and have it simply enter the stations "head-on" as it were, before reversing back out.
Innova People Movers (3 car variant) have a capacity of 200 passengers. They manage this by being significantly more spacious than the existing monorails thanks to the wider loading gauge and lack of driver cabins.
The route is roughly 1.3km long. The trains can operate at 30-40kph, which assuming a slightly lower average speed, would do the full trip in 2-2.5mins. Assuming 2min dwell times in each station (no separate cabins so boarding is much speedier), each train could make 8-10 trips per hour.
Doing some calculations for throughput on that basis, you get:
4000 passengers per hour
That's not too shabby at all for a system running just 2 trains. It's 800pph less than the old monorail (when it actually operated at full capacity) but it's far more capacity than the system has been operating at in recent years. It's also far more than the capacity of running land-trains.
Cost wise (estimates based on existing installations with inflation)
£5.8m–6.7m per 3-car train
£10m–20m for the guideway itself.
£4m–8m per station for upgrades. (accessibility improvements, building alterations & PSDs)
£2.5m–5m for automation & power supply costs.
£500k for theming (custom painted trains + new signage)
Total Up-Front Costs:
£32.6m to £54.9m
Annual Operating costs (Energy, staffing, maintenance, insurance, miscellaneous):
£1.2mm-£2m (not including closed season)
Assuming Merlin manage their contracts properly (unlike the UK government) it should be possible to keep costs down to a level no higher than £40m.
This is basically two and a bit Hyperias, so not out of the realms of affordability. Yes you wouldn't see the return on investment as quickly as you would with a new coaster, but you wouldn't have much of a park at all without a new system, so it's necessary to ensure long-term growth.
By my reckoning this is the best option for the park & for Merlin if it wants to retain the park as its premier UK attraction!
Marshy.