Your idea isn't too bad, only problem is that it is already implemented on most existing bridges and they still aren't perfect. For instance, wrapped bitcoin.
Btw, as long as it's a smart contract, there's always going to be attack surfaces.
Bridges are often expensive and there is some risk involved ,as you said .
A simple solution is to use a swap service such as exch.cx. They offer much cheaper service, as there is no bridge just 2 blockchain transactions. And the privacy is very good too
The platforms i have been using is;
Owl.to
Rhino.fi
When it comes to bridge fee then its not already shocking anymore because when you do make out that bridging on different chains then you can really be able to expect that it would come expensive specially on ETH chain? that would be surely putting up some hole into your pocket or huge deduction into your overall coin amount.
This is why whenever i do make out some conversions then i do rather make out that manual transfers on exchangers and making up some purchase but this isnt something a method that will really be also cheap and a little bit hassle yet you will be waiting up for sone confirmations.
The good thing on making use of bridges that everything is really that on one go, as long you are willing to pay up those fees then all you do need to do is to wait up until those funds will really be that making up that conversion would be finished. So far, im not that much wary about on whose the cheapest among them all, but for me the current platforms i have been using which mentioned above is already that enough for me specially on bridging transacitons.
