1. What feature do you think is missing the most?
Features that can have option to add multiple 2 Factor Authentication (2FA) in each transaction

2. What is your biggest problem with the particular wallet you use, or with the BTC/cryptocurrency wallet as a whole?
I don't have any particular problem with the wallet I'm using at the moment

3. What is your favorite wallet and why?
only imtoken and trustwallet ,

4. What changes would you like to see with the wallet you are using?
there is a direct exchange to fiat  so that you can directly transfer to a local bank

If wallets addresses can be linked with proper names, that will be beneficial. I mean if every address has an alphabetical name attached, so it will be easy to give our addresses to others if we want to receive money, and also it will reduce the risk of sending the coins to the wrong address.

Electrum has fee estimates, it can give you a rough answer how many blocks it should take for your transaction to be included in a block. But as always there's a possibility of a spike in transaction activity forcing you to bump the fee or wait longer.

I look for wallets that have coin control, LN support, ability to connect to my own node, custom miner fees, fee bumping, multisig support, and a general ease of use.

I use Cold Card for my hardware wallet, Sparrow for my desktop client, Muun for my mobile wallet for both on-chain and LN payments.

I avoid using KeepKey, Trezor, and Ledger because they have a copy of your xPub and thus know the balance of all of your addresses and which ones are yours. Super bad for privacy.

I also still use Electrum for some features that Sparrow doesn't have yet but with as fast as Sparrow is growing, I don't think I will be using Electrum for much longer simply because I won't need to. Electrum is still an excellent wallet. 

Between all of these listed above, I am able to do just about everything that I need to.

I come from a traditional banking background and was always frustrated with the limitations of bitcoin wallets. For example, many bitcoin wallets don't offer service in my local currency, which is GBP

Those changes specially in related with LN would really make a big change and would totally resolved out that issue that we do have with Bitcoin that had been always criticized.
So far aside from security then i dont see any major problems or issues with bitcoin wallets even upto todays time. For now ive been using Electrum
which does really suits out my needs most of the time. You could modify the fees and you could push up transactions when it gets stucked which does
really give out convenience.

I use Electrum wallet which is the best wallet I've used but there are some missing features I want to look forward in the future. One of it is the coin mixing on the wallet itself and of course it is much better if we can use the join coin even in small amount, though I am not really sure how things works but if it possible in the future then I really think the Electrum wallet is already perfect since it is also hardware compatible.

general noob software has too many things set as defaults and make it complicated to change. EG even core demands people 'edit file' of a config file or use command prompts. rather then having a drop down option menu.
even things like being able to manually set a fee or change the fee can sometimes be iffy to do with some wallets that prefer defaults.

...
rather then just calling all software "wallets" they should be clearly defined for their different purposes.
basically use better buzzwords/analogy words.

for instance
a hardware wallet. its just something that by itself holds the keys. so call it a 'keyring'
a lite wallet. it doesnt hold all the accounting and blockchain. so call it a chequebook
a full node wallet. being an archival node stores it all. so call it a briefcase/satchel
an exchange/custodial hot/cold wallet. call it a bank account/vault

make the names less specialist/technical/nerdy.. and more average joe friendly

many noobs are fooled into thinking a pruned node or lite wallet is the same as a full node because "wallet"
if all they care or think bitcoin is about is making transactions. they cant tell the difference. so a better average joe friendly  naming system can help create the different types of involvement and be a better level indicator by calling it names that indicate what it can handle or not... or atleast prompts people to start asking the right questions about whats the difference, rather then blindly thinking they are all the same.

EG for nearly a decade the word "wallet" for something that store keys. has been badly overused. where as keyring is more relevant. as for ones that just make transactions. because bitcoin is not a bank note but more so something that resembles the detailed required for a cheque. a cheque book would be a more appropriate term. it just confuses the noobs less by having words they can understand the purpose of.

cores software should be a full node, and they should allow other brands to be full nodes too, to reduce central points of failure. (without the political assassination attempts of REKT they done in 2014-17) . and if people want to be 'pruned' they they should download a different software which has a different useragent identifier.. so that for instance "core-lite" does a pruned version of IBD

too many noobs are fooled into thinking that when pruning on core, they are then still supporting the backbone of the network. yet reality is they are no longer part of the backbone of seeding blockdata to leachers.

i made my own. to do the tasks i need. whilst still doing the backbone stuff for network support.

for investor wallets. it could include a api call to grab the price of bitcoin on certain days and tag peoples 'received coins' with a price. and then beside it have the current price. to show the profit/loss.

for general users. better address labelling so people in a few years time can look back on their transaction history and see WHO they paid rather then just an address and having to try remembering what that address was used for

if a wallet is a multicoin/multiple network supporting software. be sure to call it that. and not some 'bitcoin layer X' software
i know people see 'bitcoin' and auto trust that if its bitcoin it must be good and trusted. but these software/altnet clients should not be auto-trusted by just bitcoin brand recognition. they should be honest about what the software does, and doesnt do

EG a good example is . although a hardware wallet was initially created for bitcoin utility, because its limit was not for just bitcoin private keys, but keys of different blockchains, they managed to call it "ledger" meaning its for all blockchains. rather then jumping on the bitcoin bus and calling it something silly like 'bitcoin physical' just for brand recognition and auto trust.

EG a bad example is. although a LN wallet can handle different coins. they want to call it 'bitcoin layer 2" or "bitcoin 2.0" just to steal some unearned trust for a wallet and network thats more buggy and faulty than bitcoin wallets/bitcoin network

The risk of malfunction is my biggest issue. I find it difficult to trust a wallet because everything is online and you can be prey to phishing anytime. I keep receiving scam links and just wonder what if I accidentally open any of them.