In the real world there are a lot of design studios that will take a classic car and add modern performance under the hood/bonnet.
A few car manufacturers are getting on in the act; Bristol Cars, Morgan and Ford.
In the whiffing world I have found that you are limited to certain scales in plastic, resin or die-cast.
Even improving toy cars seems a better solution. There's aftermarket kits available for detailing the interior, engines, tyres and body shell.
The majority are for the American and Japanese cars with a few European examples in the larger 1/24 - 1/25 or 1:18 scales.

For me Modelkcars.uk do a range of resin body shell and the Mk1 Ford Escort interior. I'm interested in the VW Beetle Estate based on the Fujimi 1/24 Beetle and the Riley Elf Transkit the Tamiya 1/24 is recommend as the donor kit.
The possibilities for a rag top for both, although I think CrayFord did this . Best check that one out.
Heinz in Wembley had a prize of 57 Wolseley Hornet convertibles. As Crayford had already produced the Mini convertible they were given the contract to work on the Hornet.

The entire Holden company

The black London cab. Instead of endless SUVs.

The Suzuki Cappuccino, but with a fully movable/retractable hardtop instead of the complicated targa roof solution that consists of four parts.
The Volvo 480.
Any microcar in Continental Europe - all major manufacturers killed them silently during the last couple of years without replacements, or they are bigger. "Costs too much", even though such small cars, with a small combustion or even an electric engine, would be more up to date than ever!

SAAB 96



Volvo Amazon

Second the Amazon! 

Trabant.  With electric power and the body moulded from something like recycled plastic bottles.

Quote from: zenrat on November 08, 2022, 02:10:15 AMTrabant.  With electric power and the body moulded from something like recycled plastic bottles.

A most interesting idea  that should please the hand-knitted muesli brigade!

 I quite like the Volvo Amazon too.  Madame R drove one for a few weeks, and reckons that you needed to be an Amazon to handle it.

Quote from: perttime on November 08, 2022, 12:00:34 AMVolvo Amazon

Quote from: Dizzyfugu on November 08, 2022, 01:21:58 AMSecond the Amazon! 

Third!

Steamers.  With today's improved technology, they'd make a right perfect alternative to either EVs, hydrogen, hybrids, or ICE.

Alcohol fired boiler would mean you could grow your own fuel.

Morris Minor.  Modern, gaudy, beefed up SUV version, with a Traveller version available with equally gaudy faux timber effect.

Quote from: perttime on November 08, 2022, 12:00:34 AMSAAB 96

In its time, SAAB 96 V4 did very well in rally and rallycross racing. When I was growing up, a business in the neighbourhood had one that looked like it was modded for the track. Sounded pretty cool too when they drove it a bit in the side street.

There were lots of 96es around then, and it had some nicknames too. "kajakki" (kayak), "syöksysämpylä" (lunging bun) ...

!976 Vauxhall Sports Hatch, not that I'm biased of course. 

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One of only 197 built.

The stillborn project  Leyland Marina Estate V8, no don't laugh they built two with the Rover V8 and MG transmission. There was also a Ute V8 but none of them ever made it onto the production line. The Australians put a 2.5L in theirs

Tell me about it! A V8 Marina did its best to kill me, but failed.

It wasn't just in an Estate body, they were going to put V8s in saloon and coupes too, but the nearest they got to 'production' were the 5-6 World Cup Rally cars, only 3 of which took part IIRC.

The one that I crashed in was a 4 door (I think...) that we were testing to measure wheel hub loads etc. and the instrumented wheel hub ITSELF failed, and the wheel and most of the front suspension took off down the MIRA 1 mile straight, leaving us behind with no means of steering, nor support for the front left hand corner of the car! It promptly turned left, went right through the Armco barrier and rolled down the embankment on it's roof......

We got out rather quickly.................