I seem to remember that RH is or was ?primarily? a boat builder? If that is the case perhaps they are more interested in boats than campers.
Perhaps they do receive offers of take-overs but can't be bothered. There is a certain mentality that says 'I wouldn't know what to do with £4 million, so I'll just carry on as I am thanks, and I've got £500,000 in the bank which will see me out. I'm not greedy for money that I have no use for".
There are a lot of 'small' fibreglass manufacturers in the country and any one of them is capable of creating a motorhome similar to RH. It would be interesting to work for AutoSleepers and get an insight into the costs involved in designing (not a lot, they do it all day long anyway), making moulds (a fair bit) and getting a new product to market (huge, I would think). You would need considerable manufacturing and marketing expertise to convert from a small fibreglass company making shower trays to one making motorhomes. Thinking about it, the staff at Lotus would probably have that knowledge. How about a LotusHome? If Maserati can make a huge 4x4 (which they do) why couldn't Lotus make a motorhome? Forget the mechanicals, they are cheap. Just buy some Berlingos or other small panel van or chassis cab and fill it with fibreglass moulds.
I would think the health and safety requirements of fibreglass manufacture must be quite stringent, I guess the chemicals are a bit iffy and it stinks to high heaven. You would need some Very Big Fans.
The trouble with a hotel is that it tends to stay in one place.