I like sidechians. It can solve a lot of problems.

Many plug-ins can be installed on top of bitcoin.
e.g.  sidechain for local economy (town, country) .. "main" blockchain can remain small

buy coffe and newspaper in local sidechain and  keep savings in bitcoin blockchain (or even Quantum computer resistant sidechain :-) )

how do you secure it?

We (I) are shorting gold from 2008
Target 200-400 for now.

So you're underwater for around 6 years?

Answer #2
5 companies or individuals create their own sidechain  (they know each others, and they sign some agreement.)

- all transactions in their sidechain must be signed with all 5 parties (POS) -> in order to add in block
- working hours 10 am - 6 pm

Edit:
a)
 - "5 companies sidechain" do not have to be public (no one knows this sidechan exists). They only lock some bitcoins into "sidechain" ... only 5 signatures can unlock bitcoins in main chain
 - they can offer to their friends/customers service what moves bitcoins  in 1 sec to any other of their customer  (only 5 signatures are needed to confirm transaction in sidechain)

IBLT kicks most of the scalability argument for sidechains into touch and out of bounds.

Sidechain offers much more than scalability.

- Assurance contracts
- Time-shifted fees
- Demurrage
- Subsidy
- Co-signed SPV proofs
- SNARKs
- ...

and all possible combination  :-) (endless opportunities)

Edit:
While main protocol intact. No one have to bother with sidechain. Only use if you like feature of sidechain.