I would definitely stick with the meme positionning.
1. Crypto is, and will stay for some more years, a nerd network. We all know our parents or friends won’t be using flashstaking (or even bitcoin) before years.
So we don’t need to target the mainstream who needs to be secured, but only the crypto users who already is in the meme culture
2. A strong identity creates more brand memory.
Right now, on the web every websites looks like any other, with the flat design stuff. It’s hard to be distiguished. We have the opportunity here to create something very different, that people will then remember. Being remembered means people will think about us, and come to use us
3. A strong identity helps fighting against copycat
We all know that if Flash is a success, lot of similar projects will pop up in the second.
Having a very strong and memey identity will help us to fight them, having both the protocol AND the branding versy strong. It will make harder for other projects to compete with us.
4. A “back to the future” theme help installing the flash key concept
The team loves the “time travel of money” and I think they will keep it.
Having a design that goes deep into this very same way will help people remember the USP (Unique Selling Proposition) of Flash: giving you your reward before you have to wait.
That is great.
They are so many protocol people don’t understand or forget about why they are built for.
Here, people will remember easily.
5. Most DeFi websites are… weird.
We all know the Uniswap Unicorn.
Have you been on Curve? Harvest? Aave builds everything about the ghosts.
Very strong DeFi protocoles uses memes and people keep using and loving them.
Doing something boring won’t make more people use our service.
Degens are not afraid by Doloreans 
6. UX is key
I think the whol thing will be finding the right balance between the meme and the usability.
Too much weird stuff might make it harder to use.
Let see what can be done to find the right balance.