A few facts to chew over:-
The devolved Parliament in Edinburgh only controls areas of responsibility handed down to it by Westminster and decides how best to do this when spending money from the block grant settlement it is given. If it decides to build a Parliament or meet NHS charges it does so by cutting others areas of expenditure. We get to vote on their performance at Scottish Parliamentary Elections with one fast approaching, hence the usual bribes and "blue sky" thinking (local Income Tax, Scottish Government Bonds etc).
A local Income Tax is unworkable unless the Scottish Government pays HM Revenue & Customs to install the Computer technology to allow this to be done. So far it has chosen not to do so.
We have both employers and employees in Scotland whose tax records are with Tax Centres down south and vice versa. Then we have Public and Private Sector organisations with employees on both sides of the border. Different tax rates in any form would be a nightmare to administer. Tax avoidance would be even more widescale.
Even if the mechanics could be sorted out, do you think Scots are any more likely to vote for a voluntary Tax rise than others in the UK?
When most Scots vote SNP they are not voting for Independence but just giving Labour a kicking. Why? The Conservative Party in Scotland shows no sign of ever recovering, the Liberals only have a significant power base in the Borders and Northern Isles (Orkney and Shetland) and may now have risked that by joining the current Government. This year it may be more of a fight between SNP and Labour with the latter likely to come out on top but possibly in coalition once again with the Liberals!